implement revert() for all element types and use that in setVolumePositive()

- setParameter in MVertex
- revert() for quad
- minor cleanups in I/O code
- start work on overlap mesh in fourierModel

finish BDF reader for 2nd order elements

added routines output (incomplete) second order elements in BDF

SAME REMARK AS WITH UNV: PLEASE TEST THE NODE ORDERING

make reading code a bit more compact by consolidating getVertices() in a
single routine

added full support for incomplete second order elements (8-node quad,
20-node hexa, 15-node prism and 13-node pyramid):

- second order generation algorithm can now be told to generate either
  complete or incomplete elements

- MSH I/O routines can deal with all elements

- UNV I/O routines now support all the elements in the I-deas spec (I did
  my best to follow the spec for the ordering of the nodes, but I might have
  made some mistakes: PLEASE TEST IF YOU HAVE ACCESS TO A CODE OTHER THAN
  GMSH THAT CAN READ/WRITE UNV FILES)

- Use correct vertex ordering for second order simplices in UNV format
(thanks to Romuald Conty <conty@phimeca.com>)

- MLine2 -> MLine3

better fix

fix crash when adding a geo entity while a mesh is displayed

removed "primarily Delaunay" from the docs ;-)

- start work on fourierModel
- add support for pyramids in BDF (it's not in the official spec I have
  here, but all the files I found on the web use CPYRAM)

changed name of second order elements (in prevision of addition of standard
new ones like 8-node quad, 20-node hex & co)

make sure to null-terminate tmp string

generalize BDF vertex reading code to handle the special Nastran floating
point formats (-1.-1 == -1.E-1, etc.)

use atof/atoi in simple cases

- finished Nastran BDF implementation (read+write in all BDF formats:
  free field, small field & long field)
- improved UNV and Medit import
- added detection of bad vertex indices in all import routines
- fixed bug in 2nd order quad constructor

- changed UNV output to match MSH output w.r.t. physical groups
- new UNV file reader

add CBAR for lines in BDF

make clear that we only read/write "free format" BDF files, with a comma as
the separator symbol

make sure we store all types of elements

make all dialog windows resize correctly with the font size

use MSH version 2 by default

Added support (both read and write) for the Nastran Bulk Data File
format (BDF).

This might need some adjustments depending on what the actual spec
is: I just reverse engineered some BDF files I found on the web :-)

refer to .mesh as MEDIT format, not INRIA format

store partition number as a short (instead of a full integer)

set the 2 padding bytes in binary STL to 0 (it's just cleaner)

missing activate_cb string for general transformation button

put fltk popup bug fix in a single header file