- replaced old 2nd order views with new adaptive stuff (still missing
  some function spaces for quads/hexas)

Added ability to "sacrifice" higher dimensional generators of
homology groups in order to compute lower dimensional generators faster.

Added "#if defined(HAVE_KBIPACK)" preprocessor directives to only enable
homology plugin & compile the code when kbipack & gmp library is avaible.

Added Geo/Homology.h and Geo/Homology.cpp as mid-interface for homology
computation (the role of utils/misc/celldriver.cpp so far). From there on
it's easy to either make plugin interface or parser interface, or both.

Made Homology Computation plugin usable.

The IO & graphics for post-processing views of the results of the homology
computation are crude at the moment: it saves the results to a separate
.msh file and reads them back by merging that to the current Gmsh session
(it uses File->Merge method).

  the .msh format -> bumped version from 2.0 to 2.1)
- move createTopologyFromMSH into GModel.cpp (and renamed to
  createTopologyFromMesh)

- display all control points in GUI for gmsh curves
- uniformize Fl_Value::step() values in GUI

- simplified background drawing (+added option to use jpeg/png image)
- better default clipping planes

added simple Helhmoltz solver + demo finite element plugin

Removed GSL dependency. Gmsh now uses blas and lapack for linear algebra
stuff.

moved all string options to std::string

*****************************************************************
WARNING: this has the potential to break things in subtle ways...
         PLEASE TEST AND REPORT ANY WEIRDNESSES
*****************************************************************