csd solver added

See merge request !14

fixed funny fix, where vtk gave a off-by-one array size back (replaced getarraysize with getnumberofcells)

fix indexing bug for StringListOptions

See merge request !12

Code restructure

Closes #35

See merge request !11

# Conflicts:
#   code/src/mesh.cpp

# Conflicts:
#   code/include/mesh.h
#   code/include/quadratures/quadraturebase.h
#   code/include/settings/config.h