Review Request: loading JCE providers using ServiceLoader

[Sean Mullan]

Please review my code changes to enable JCE providers to be registered and
loaded as services using the ServiceLoader API:

http://cr.openjdk.java.net/~mullan/jigsaw/webrevs/jce-service/webrev.00/

There is one outstanding issue that needs to be resolved, but I think we can try
to resolve this later:

You cannot load more than one PKCS11 provider (ex: with different
configurations), as currently supported and documented in the PKCS11 guide [1].

Thanks,
Sean

[1] http://docs.oracle.com/javase/7/docs/technotes/guides/security/p11guide.html