removed set_email and update_email from actions, they were removed eons ago.
removed unsubscribe_update and request_update also removed long ago
added protected method only_admin to make default policies simpler
added update_password to actions list
added user policy to the project
migrated users controller to pundit
removed cancan user abilities
uservoice_gadget won't need any privilege
migrated user views to pundit
Merge pull request #560 from diogob/migrate_users_to_pundit

Migrate users to pundit