Deleting users from Omeka wo removing from DS breaks project

[mebrett]

If you delete users from Omeka S without first removing them from their projects, it breaks the add/remove users functionality on that project such that you can no longer add or remove new users for that project.

[jmotis]

This has now been documented at https://github.com/chnm/Datascribe-module/wiki/Projects#deleting-users but leaving this issue live in case it is possible to fix this bug in the future.