Expand C-interface to more classes

[hverhelst]

ADD:

• gsBoundaryConditions
• gsFunctionExpr
• gsNurbs
• gsGeometry::degreeElevate
• gsKnotVector several members
• gsMultiBasis
• gsSparseMatrix

[hverhelst]

In this PR the ubuntu run fails becuase of some Fortran issues. This is the output:

/usr/bin/ld: optional/gsCInterface/CMakeFiles/gsCInterface.dir/src/Fgismo.F90.o: in function `__fgismo_MOD_f_gsmatrix_print':
/home/runner/work/gsCInterface/gsCInterface/gismo/optional/gsCInterface[Fgismo.F90:488](https://github.com/gismo/gismo/blob/20886849ffb7aa6784236405ee70506a593a5cc5/Fgismo.F90#L488): undefined reference to `_gfortran_st_write'
/usr/bin/ld: /home/runner/work/gsCInterface/gsCInterface/gismo/optional/gsCInterface[Fgismo.F90:488](https://github.com/gismo/gismo/blob/20886849ffb7aa6784236405ee70506a593a5cc5/Fgismo.F90#L488): undefined reference to `_gfortran_st_write_done'
/usr/bin/ld: optional/gsCInterface/CMakeFiles/gsCInterface.dir/src/Fgismo.F90.o: in function `__fgismo_MOD_f_gsvectorint_print':
/home/runner/work/gsCInterface/gsCInterface/gismo/optional/gsCInterface[Fgismo.F90:334](https://github.com/gismo/gismo/blob/20886849ffb7aa6784236405ee70506a593a5cc5/Fgismo.F90#L334): undefined reference to `_gfortran_st_write'
/usr/bin/ld: /home/runner/work/gsCInterface/gsCInterface/gismo/optional/gsCInterface[Fgismo.F90:334](https://github.com/gismo/gismo/blob/20886849ffb7aa6784236405ee70506a593a5cc5/Fgismo.F90#L334): undefined reference to `_gfortran_st_write_done'
/usr/bin/ld: optional/gsCInterface/CMakeFiles/gsCInterface.dir/src/Fgismo.F90.o: in function `__fgismo_MOD_f_gsvector_print':
/home/runner/work/gsCInterface/gsCInterface/gismo/optional/gsCInterface[Fgismo.F90:198](https://github.com/gismo/gismo/blob/20886849ffb7aa6784236405ee70506a593a5cc5/Fgismo.F90#L198): undefined reference to `_gfortran_st_write'
/usr/bin/ld: /home/runner/work/gsCInterface/gsCInterface/gismo/optional/gsCInterface[Fgismo.F90:198](https://github.com/gismo/gismo/blob/20886849ffb7aa6784236405ee70506a593a5cc5/Fgismo.F90#L198): undefined reference to `_gfortran_st_write_done'
collect2: error: ld returned 1 exit status

@eve70a @filiatra do you know an easy fix?