Training Permissions

[wgj]

Create or update the role for trainers. Trainers are the boots on the ground for TA

A trainer can:

• change attributes of a training object where they are listed as a trainer
• flag Students of a training object where they are listed as a trainer, and the student is listed as a student

[flwyd]

Combine this with issue #8 and issue #9 as a conceptual task for handling all training-related permissions.