AddPermissionLevel overrides to allow extra roles

The Add Permission Level calls used to work with a RoleType but that doesn't allow you to be able to add Approve or Manage Hierarchy rights. I have created some overrides which allow you to specify a role definition name. e.g "Approve", "Full Control" etc. Updated tests to match. Also added a test against a Finnish language site and it still seems to work with English role def names so looks like language isn't an issue.