added small warning in automatically generated opt_* files

- 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)

- new "Delete Empty Views" command
- new View.MinX, View.MinY, View.MinZ, View.MaxX, View.MaxY, View.MaxZ options
- added example on how to do simple volume visualization

The "Simplex" class is now derived from a new class "SimplexBase",
which contains only pointers to the nodes, and none of the other stuff
necessary for the actual mesh generation.

All the input/output/display routines have been rewritten in terms of
SimplexBase: this provides a gain of almost 50% in memory when you
just load meshes from .msh files to do visualization stuff, instead of
actually generating the mesh.

forgot to update help strings

airplane work: reorganized the option panels in the GUI (more descriptive
labels, same categories for geo/mesh/post, etc.)

- added an option to draw the bounding boxes

- simplified the color_scheme options

- added tooltips to make the discovery of shortcuts easier

mesh smooth normals

forgot this one

update doc for vertex arrays

- only save the options that differ from the default values (unless we
  explicitly ask to save everything)

- tweak the auto doc routines

- cleaned up the octree code (renamed some files, added copyright
  notices, indented everything)

- backported JF's doc from the texinfo file into the c++ code (the
  documentation is actually generated automatically by Gmsh with
  "gmsh -doc"!)

- replaced nPoints with nPointsU and nPointsV in CutGrid

- fixed a couple of printfs + removed some unused variables

And more airplane work!

- merged STL patch from Nicolas Tardieu. This patch permits to
  create an real elementary surface for each STL face. Until
  we have some code to directly remesh the STL data (which would
  be much nicer and cheaper), this is very useful. We can finally
  use STL representations to create meshable volume models.
  Thanks Nicolas !

- new option to color the mesh by physical entities (if an element
  belongs to multiple physicals, we use the first one)

- additional cleanup of the mesh drawing code

- big cleanup of the geometry creation section in the parser:

  * removed horrible Geo/DataBase.cpp
  * fixed all List-related memory leaks (a lot!)
  * added tests to check if we don't try to recreate existing
    entities (this should prevent many weird bugs due to incorrect
    input files)

- fixed LineLoop/EdgeLoop memory leaks

- many small fixes all over the place

More "airplane" work...

- rewrote the way we handle lights: glEnable(GL_LIGHTING) is now used
  at the lowest level, where it belongs. This fixes many lighting
  glitches, and should make the whole stuff much more predictable;

- simplified the display modes for geometry and mesh: the choice
  between wireframe/solid is now independent of the choice of
  lighting/no lighting (and there is a new "Enable lighting" option
  for the geometry, too--even if it does only affect things like
  normals/tangents at the moment);

- brand new code to draw really nice (shaded) 3D arrows + 3 options
  that fully parameterize them (they can degenerate into pyramids,
  cones, w/ or w/o stems, etc.);

- new options so that we can also use the new arrows outside the
  post-processing module (e.g. for tangents/normals).

- "alt+d" now simply switches between solid and wireframe mode;

- new shortcut "alt+w" to switch the lighting mode for all the modules
  (geo/mesh + all post views) at once.

bring option docos up-to-date

Add DisplacementFactor option + rename ArrowScale->ArrowSize and
ArrowType->VectorType

Small corrections

Corrections apres relecture / part 1

More work on chapters 1 and 2. Should be mostly OK now.

Major rewrite of the Overview section + web page

small updates

Added "gmsh -doc" to automatically generate the texinfo documentaion
for all the options.