Facilitator mode

[vtestagrossa]

Create different authorization routes to handle ownership of the groups. There should be editable cards, fields, and boards on the home page for the creator of the group, and others should just be able to select their group until they've selected one that belongs to them.

The session variable facilitator needs to be set on a per-group-selected basis.

[vtestagrossa]

Authorization routes are now able to be handled with the authorized function within common_model.py, which takes two functions as arguments and returns the first if authorized, or the second if not.