Added possibility to change forces from ActionAtomistic
Added fit to template
POSITION CV

It works. However, it should be used after FIT_TO_TEMPLATE.
I think it should not be merged until a test that enforces
this has been implemented.
Added warning on POSITION
Merge branch 'fix-98' into v2.1
Added SCALED_COMPONENTS to POSITION
Added more doc
added regtest for POSITION and FIT_TO_TEMPLATE
changelog
Merge remote-tracking branch 'origin/v2.1' into v2.1