separate multistep, multipartition datasets)

Changed homology generator chain mesh element orientations (determined by vertex order) so that
post-processing data isn't needed to save the generators, instead all the
elements have coefficient 1 now in the chain. Due to this also reverted
changes made to GModel writeMSH method in my earlier commit (they became obsolete).

entities.

Added option to save MSH without renumbering the mesh elements (required to
save post-processing $ElementData right!).

added GModel::getMeshElementByTag (uses a dynamically created cache, like
what we do for mesh vertices)

- moved GUI to FlGui + added experimental QGui to test Qt

- fixed most MSVC and gcc compiler warnings

- converted some remaining tabs to whitespace (that's why the patch is
  so large; please try to remember to indent with 2 spaces and not
  tabs when you commit stuff to CVS)

- merged modified patch from Konstantinos Poulios to allow saving
  physical/partition as element tags in mesh formats that don't
  support them natively

- unstructured mesh algos (+ refs)
- interpolation matrices in .pos format

HAVE_XXX defines.

This fixes three longstanding problems:

- the API was hard to use because some headers had HAVE_XXX ifdefs, so
  that cient codes had to know how the lib was compiled to compile
  themselves

- we had to do make clean after each ./configure, which erased too
  much (e.g. most of contrib)

- make depend could include unwanted stuff since it redefined FLAGS

- fix bb computation to avoid model jumping around when adding points in z=0 plane
- pass interpol matrices as ref

- fixed missing getShapeFunction/getGradShapeFunction + return all sf
  at once so we can implement MElement in term of these consistently
  (w or w/o FunctionSpace)

- can now merge multiple meshes and remove duplicate mesh vertices
  (useful e.g. when merging several STLs)

- added easy interface to create model-based postpro datasets on the
  fly + use this for mesh quality stats

* add lc_extend_from_boundary in GUI

   1) this removes the asymmetry in all the routines involving mesh
      elements associated with points

   2) it makes it possible to use point-based datasets in the
      model-based post-processing module

  **********************************************************
    PLEASE TEST --- ESPECIALLY THE INPUT/OUTPUT ROUTINES!
  **********************************************************

* made GModel::getEntities() more efficient and generalized its use

  did in high
* added mesh generation error log summary
* removed Parallel subdir (this is now handled by the message class)
* removed Box subdir and consolidated batch processing in a single
  routine
* made List_T into a class
* reduced dependencies in Pview*.h so we can eventually add the post-pro
  interface to the public API

arghh, MED 2.3.3->2.3.4 changed the name of the enum MED_NOEUD_ELEMENT into
MED_NOEUD_MAILLE !

- separate setNode and tagNode in API

  integer tags per step data
- ported Eigenvectors and StreamLines plugins to the new post-pro API

- ported Gradient, Curl, Divergence, Integrate and Transform plugins
  to the new abstract post-pro API

- documented new post format