Remove assert check for locking from ServiceControllerImpl.isMode
Make service removal revertible
Move check for critical problems to AbstractTransactionTest.commit, thus garanteeing that a complete output/failure message will always be showed for tests that fail to commit a transaction
Make registry enabled/disabled feature work on revertion cases.

This avoids a race condition where a service controller misses an important notification because it was removed/reinstalled in a window of time where registry was enabled/disabled.
Make InvalidTransactionStateException message more human-friendly, explaining the exact reason why a transaction cannot be committed
Replace Transaction.commit check for PREPARED state by a check for FLAG_PREPARE_REQ. This avoids forcing the user to wait on prepare completion before committing.
WIP Make service installation revertible