Associate ConCat roles with Tracker roles

[Gawdl3y]

In order to simplify management of users in Tracker, roles should be able to be automatically assigned to users based on their ConCat role when logging in. Ideally, there would be a UI to manage these associations so that multiple roles in ConCat could be assigned to the same role in Tracker. #18 is related, but not necessarily a blocker for this.