Fixed BugreportController and ExerciseController

Fixed both controllers to use the new UnitOfWork and Repository
patterns.
Fixed another but in the ExerciseController

Forgot a syntax error.
Fixed ForumController

ForumController is using the Repositor and UnitOfWork patterns now,
aswell.
Fixed HomeController
SessionController is fixed now, too.
Fixed UserController

UserController compiles again, but it still needs some more work.