Form factors: addition of appendix to User Manual, schematic views and missing information to Doxygen

New doxygen docs switched on, Doxyfile.in is introduced for automatic propagation of version number in the project.

- no latex output
- html output goes to BornAgain/html

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

On the way to add roughnesses of layers: new classes IRoughness, LayerInterface, lots of comments and const references. New Doc/Doxyfile for oxygen generation.