Add __str__ methods to the member models

Thom Wiggersrequested to merge
add_strs_to_member_models into master

Previous behaviour

Steps to reproduce:

  1. You'd get the default __str__ to show up in various places, e.g. headers of Membership blocks on the User page in the admin or in the history.

New behaviour

Steps to validate that it works:

  1. See that it's all pretty now.

Merge request reports