Add command to fix ZA PositionTitles

This adds a command which updates all Positions with the PositionTitle 'Party Member' to have 'Member' instead, then deletes the Party Member title. For #1153
Rename'Party Member' roles to 'Member'

For #1153. Party Member is superfluous, they're Member's of a party, so we can work it out.
Merge branch 'master' into staging-auto-deployed