Pre-validate paths for unregistered namespaces

- Add FedoraInvalidNamespaceException type
- Add FedoraInvalidNamespaceExceptionMapper
- Add new validatePath method to AbstractService
- Fix Unit Test that require a mock NamespaceRegistry

Resolves: https://www.pivotaltracker.com/story/show/61500426
Cleaning up Java compiler warnings
Merge pull request #482 from ajs6f/TooManyExceptions

Cleaning up Java compiler warnings
Merge branch 'master' into master-aic