Added Fourier transformed 2d Gaussian; removed strange looking denominator in InterferenceFunction2DLattice.cpp; regenerated python API

PythonAPI now hanbdles pure virtual method automatically, so should be save to use pure virtual in our CPP interfaces

Remove transformation from FormFactorCrystal; transform Lattice and LatticeBasis instead of q for form factor calculations; rotate mesoformfactor also

Make FormFactorDecoratorMaterial owner of (transformed)material; updated python API; removed transformation from FormFactorCrystal::evaluatePol; clone IMaterials

MesoCrystal test is off, new fitting examples for spheres in a lattice and corresponding changes in visitors

Implemented automatic propagation of BornAgain version number via cmake. Version must be defined only in the file cmake/modules/BornAgainMacros.cmake.