TRUNK-4411 Relaxed ProviderValidator to accept duplicate identifiers.

- Removed the uniqueness check in the validator.
- Fixed ambiguous java docs (and fixed an error in the documentation).
- The validator only checks for the presence of a retired identifier(with reason for retiring).
- Removed test for unique checks as this behaviour is no longer supported..
- Renamed and fixed tests to accept duplicate entries for Provider identifier.
TRUNK-4411 Relaxed ProviderValidator to accept duplicate identifiers. Updated test names and should annotations.

 - Made them more consistent.
Merge pull request #983 from chocobar/master

TRUNK-4411 Relaxed ProviderValidator to accept duplicate identifiers.