MDS-488: couples move constructor was implemented

gcc 4.4 does not implement move constructor by default, so we need to do
it explicitly
Version up to 8.23.5
Set free_effective_space will be set to zero if it's not provided
Merge branch 'feature-free-space' into development
User settings API was added
Ns_state::weights does not need groups-count to give groups
free_effective_space method is added into ns_state
Merge branch 'feature-mds-437' into development