Group management

[max-zilla]

PR touches a few things:

• add GroupAuthorization dependency that enforces group members/editors/owners
• use Provenance in groups model
• improvements to several auth/groups endpoints (some were not functioning properly)
• new endpoints for setting user/group roles on a dataset
• new endpoints for adding/removing user from a group
• create test utils file with some shared JSON - need to continue to leverage

[longshuicy]

Any reason you leave the group_id out of the path parameter?

[max-zilla]

no that was not intentionally removed, fixed thanks

[tcnichol]

I created several groups. One user shared datasets only by group. The correct users can view/edit etc datasets and only the group members with roles 'editor' were able to add new group users. Everything seems to work here so marking approved.