polish the last commit some more (activate/deactivate widgets, etc.)

a little more work on the axes stuff: enable global axes for the geometry and
the mesh, too. We can finally get rid of the ugly old "moving axes" bit.

(+ reverted changes in unproject: need to be more careful since unproject
can be called outside Draw())

- added an option to force the size/position of the 3D grids/axes

- cleaned-up the whole size/position thing of 2D/3D grids: it's much
  more consistent now (and the GUI is nicer)

- rewrote the algorithm for automatic positionning of 2D graphs (now
  they rescale with the window, which is much nicer--and far more
  practical)

- cleaned up (somewhat) + finished the euler angles/quaternion handling

- added a new little dialog in gui to specify the rotations/scales/translations by
  hand. This is similar to what I did in the Motif version of Gmsh a looooong time
  ago, and I was really missing this capability... (e.g. being able to specify
  exact rotation angles)

- the grid options now also apply to 3D views (this way we can
  finally get accurate size info for any data set; and the info
  is updated in real-time for gemeotry transformations & displacement
  maps)

- new option to specify the size of the moving axes

- generalized text align code (we now support the 9 modes that TeX
  does)

change sign of levelset so that the iso-volume is more natural

Plugin(Extract) can now also extract data from a specific time step

Generalized Plugin(Extract) so that it can also create tensor views

small generalization: we can now interpolate data from abritrary
views (and not only from views having the same data type as the
destination)

I use this to interpolate (combination of) components of a field
in one mesh onto another mesh, for example a set of isosurfaces
from another field. Wicked cool! ;-)

small doc fixes

- generalized the octree code to make it work with all the element
types, and not only with triangles/tets (and fixed a couple of copy &
paste bugs in the process...)

- modified all depending plugins to take advantage of this

change the behavior of "-string string" command line option to match the
bahavior of "-option file"

- New "Discrete Line" commands (similar to the Discrete Surface commands, but for
  curves).

  This permits e.g. to use Gmsh's extrusion mesh generators on 2D meshes (with
  boundaries) imported from other programs, and have all the useful elements
  generated (both volume and surface).

- Don't use Ctrl+m for File->Merge, as it is a reserved keyword for
  Window->Minimize on OS X:
  * File->Merge is now Shift+Ctrl+o (since it's in some way a variation of
    File->Open's Ctrl+o)
  * Tools->Options is now Shift+Ctrl+n

add "Window" menu on Mac OS X

mention python

- added new "spectral" colormap (truncated hsv)
- added GUI button for elliptic mesh + geometry coherence
- added GMSH_MAJOR_VERSION, GMSH_MINOR_VERSION and GMSH_PATCH_VERSION
  in the parser

Adding python solver interface from Carl Osterwisch <osterwischc@asme.org>.

The interface comes with a example python "solver" that converts an Abacus
result file (in CSV format) into Gmsh post-processing views. Very cool ;-)
Thanks Carl!

typo

better Tools->Visibility GUI

use C++ example in doc instead of C

- renamed "Duplicate View" into "Alias View" (suggested by Philippe;
  less confusing since "Duplicate" implies that we actually copy the
  data, which is not what we are doing)

- added general "on the fly" tranformation matrix option. This allows
  for very efficient visualization of aliased datasets with
  non-destructive rotations, symmetries, etc.

help should mention that iView and ExternalView have to be of the same
type (scalar, vector or tensor)

new plugins: Gradient, Curl and Divergence

pretty print

typo

- generalized Plugin(CutGrid):
   * now works also for lines/points (i.e., when nPointsU and/or nPointV == 1)
   * new option ConnectPoints

- new Plugin(Eigenvalues)

- don't force color in Draw_PlaneInBoundingBox

- removed all the crappy STL code and rewrote it using JF's POLY_rep
  class

- generalized POLY_rep so that we can use the polygonal discretization
  as a surface mesh, and mesh in 3D afterwards. I.e., we can now take
  an input triangulation (a single surface in STL format, multiple
  surfaces in STL format, one or more surfaces defined using the new
  "Discrete Surface" commands), and generate a 3D mesh that uses it. We
  could in theory even mix triangulated and "normal" surfaces in the
  same geometry, but nothing is done at the moment to ensure that the
  mesh at the interfaces would match (if it does, it actually works
  very nicely)

- new STL mesh output format to export a surface mesh as a STL file

- added an option to the GEO output routine to save the surface mesh
  as discrete surfaces associated with the geometrical surfaces

- added STL and Text output formats for post-processing views (the
  text output allows for example to exploit plugin-generated data in
  gnuplot)

- generalized Plugin(Evaluate):

  * can loop automatically over all the timestep and/or components

  * can do operations using data from an external view

     - if the 2 views are based on the same grid, the plugin does the
       evaluation very efficiently

     - if the 2 views are based on differenet grids, the plugin
       automatically interpolates the external view data onto the
       grid of the current view

- added new Rand() function in MathEval

- default colormap is now # 2 (the Matlab "Jet" colormap)

Generalized the Levelset routines so that we can compute isovolumes with
all levelset-based plugins. This allows to extract either side of a
levelset (i.e., a half space with CutPlane, the interior/exterior of
a sphere with CutSphere, or the isovolume inside an isosurface with
CutMap).

add option to specify the size of the small axes

add special token "Today" to return the current date

fix small mistake in definition of char-expression

copyright update

- More intelligent way to detect if we need to apply a polygon offset
or not.

- better computation of translation coef in Draw2D

Ctrl+a->Shift+a

Small aesthetic changes:

- Only 'title-capitalize' window titles and menus; the rest should be
  capitalized like normal english sentences

- The window title should be exactly the same as the menu item
  (without the ellipsis character if there is one)

Print "Shift+Ctrl" instead of "Ctrl+Shift" in the docs, since this is the
way both FLTK and MacOS do it