Add help text to MS_phasevels
Add help text to MS_phasevels

and give error() two arguments.

pusher96/MSAT,pusher96/MSAT,jwookey/MSAT,pusher96/MSAT,alanfbaird/MSAT,jwookey/MSAT,alanfbaird/MSAT,jwookey/MSAT,alanfbaird/MSAT