more work on levelsets & co

- 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

  buggy)
- small doc updates

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

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

move integration routines to Numeric/