Remove Organization and Team models from Lastuser

[jace]

Remove Organization and Team models from Lastuser

[jace]

Counter-proposal: remove only Team for now. Organizations are widely used, so attempting to remove them will require a transition period lasting months. Teams, in contrast, are only used in Kharcha and Funnel, so their removal will be simpler.

If organizations are removed, usernames must be removed from Lastuser as well. Attempting to do username management between Lastuser and a client app is asking for trouble.

#118 already discusses a pathway for replacing teams with roles. There is a concern there about userids for teams and Flask-Lastuser. Temporary workaround: every organization has two uuid columns to represent owners and members, and the API passes these on in place of teams; all other teams will be deleted.

[jace]

The ideal path is that both Organizations and usernames move into Funnel, and that Flask-Lastuser is updated to transparently query Funnel instead of Lastuser. This minimizes disruption to other apps. However, we need a transition pathway to give Funnel breathing room to find an appropriate implementation, so it seems prudent to start with paring down functionality in Lastuser.

[jace]

Organizations and teams can be marked as deprecated in Lastuser once Funnel rolls out membership models into the master branch via hasgeek/funnel#401.