* Added views and controllers for users and roles.
* Further implemented membership and roles provider functionality and added some test cases for it.

[fixes]
* If new role is created and no navigation exists for it, the user is presented with the option to create it.
* Repository.BeginTransaction method will do nothing if a transaction is already active. (it was trying to create a new transaction before)

[db changes]
* role deletion is being cascaded to delete its navigation
* navigation deletion is being cascaded to delete its items
* added unique constraint on role names per tenant
* user-role relation is being deleted when either the user or the role is deleted

[other]
* added backbone.marionette v1.0.0-rc6 for future use
Patch for previous commit (forgot to commit the db changes).
Small work on roles.
minor tweak for multi-tenant membership provider
minor tweak for multi-tenant membership provider
Merge branch 'users'