Major work on GUI : removed much-hated "menu window" & merged onelab tree in graphic window. Gmsh now requires FLTK 1.3.

(Additional changes: fixed crash when de-minimizing opengl window on mac os ; refactored Msg::StatusBar)

To abort a script, use "Abort"

Better handling of (co)homology computation in selected dimensions only. Various cleanups and documentation of (co)homology stuff.

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Added possibility in homology solver parser interface to select (co)homology space base dimensions to save; Added option to select (co)homology basis physical groups numbers and debug options to HomologyComputation plugin.

fixed nasty bug in quad meshing
added parameters to BL generation (2D)

Make sure to close the files left open (on purpose) in ParseFile when we exit OpenProject or when we call ClearProject.

Leaving the files open can lead to file handle exhaustion, e.g. with onelab when remeshing several hundred times. This then leads to
unpredictable socket errors.

First pass at cleaning up lists in the .geo parser: 

- we now keep track of the variable type ("list of floats" or "single float")
- the brackets [] after the variable id are now optional (aa={1,2} == aa[]={1,2}) when creating a new list
- the old syntax is kept to enable forcing the type to "list of floats" when creating a single-entry list
- on single floats, += performs the usual arithmetic operation; on lists, += appends to the list (idem for -=)

WARNING! this is a possibly dangerous commit: please test your .geo files and your scripts and signal any weird behaviour

Added option for levelset cutting ""CutMeshTri(tag)", that saves only triangles and tets (no polygons or polyhedra)
Added new level set definition "Levelset Points(tag)={{x1,y1,z1},{x2,y2,z2}};", builds a level set from a set of data points using RBF interpolation