Issue #9 cross framework library refactoring
- Moved TresholdsGovernor, RequestCountsRepository from
AuthenticationGuardBundle
- Corrrected namespaces and use statements 
- Result\Rejection and subclasses added, corresponding to
AuthenticationGuardBundle\Exception\AuthenticationFailedException
- TresholdsGovernor::checkAuthentication now returns null or
Result\Rejection
- moved actual tests from AuthenticationGuardBundle to
Tests\Service\TresholdsGovernorTest
	(tests require injection of properly initialized TresholdsGovernor)
- adapted TresholdsGovernorTest to
TresholdsGovernor::checkAuthentication returning null or
Result\Rejection
- added documentation (2B completed)