- Documentation can now be built by command 'make doxyuser'
- configured doxy files now in build/doxygen (no longer under version
  control)
- html output now under html/build

- rename flag BORNAGAIN_RELEASE -> BORNAGAIN_CONFIGURE_DOXY
- write configured Doxyfiles to auto/Doxygen

Doxygen: changed output dir to html, BORNAGAIN_PYTHON definition added, @brief propagated to class method list

the remaining Doxyfiles write to subdirectories html/std, long, dirgraphs

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

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