Added generation of DM variations
Vim-backup did not have the frequency component added in add_dm
Merge pull request #1 from vhaasteren/dmvtoasim

Accepted for now
Added freqSSB (may be temporary name)
Merge branch 'master' of https://github.com/vallis/libstempo
Merge branch 'master' into tempo2-cvs
Added generation of dipole GWB distributions in the residuals
Updated the GWB dipole simulation code