changes to Packages and Speed doc files

Resolve object dependency problems for CMake build system

CMake updates

SPIN package fixes, especially for DMI

Coverity inspired fixes to BODY package

- improvements documentation (dmi and exchange)
- correction error cross product in pair_spin_dmi.cpp
- implementation mech. part in pair_spin_dmi.cpp
- correction in all pairs: init_one for [j][i] couples
- correction in atom_vec_spin.cpp: index error in read_data
- some improvements in pair_spin_dmi.cpp and pair_spin_magelec.cpp

changes to Errors and Python doc pages

doc changes for Examples and Modify sections

Re-allow commands after an exception was caught inside a run.