OR-723 Augment PUT /communities/:id/members/:user_id with community manager actions
OR-723 Update error messages
Merge pull request #496 in OR/rse from OR/rse-chamerling:OR-723 to master

* commit '4211399ac73fec1168327721e153b849fce2ccb8':
  OR-723 Update error messages
  OR-723 Augment PUT /communities/:id/members/:user_id with community manager actions