Domain API for Rackspace Cloud DNS.

@adriancole Here it is. This has almost all :) of the changes we discussed on IRC on Saturday. Please review. There are several things of note.

* The build will probably fail because https://github.com/jclouds/jclouds/pull/1460 hasn't sync'd to sonatype yet. I've been watching https://oss.sonatype.org/content/repositories/snapshots/org/jclouds/api/rackspace-cloudidentity/1.7.0-SNAPSHOT/ and https://oss.sonatype.org/content/repositories/snapshots/org/jclouds/api/rackspace-cloudidentity/1.6.0-SNAPSHOT/ but nothing yet. I'd like to get feedback on this code sooner than later though so I'm forging ahead.
* Ignore the Records stuff. I just had to stub out a few classes and methods to make sure I was on the right track.
* I didn't remove the Subdomain stuff. It was already in there and working and convenient. :P Have a look at it in its entirety and if you feel it should still be postponed, I'll take it out.
* Have a close look at DomainApi.update() and DomainApi.delete(). Notice how I don't specify a type for Job (hence the SuppressWarnings). This is not good but I wasn't sure what else to do. In these cases Job doesn't return a useful response so I'm only interested in the Status. I don't care about the type so I don't set it. What should I do here?

To run the live tests:

    mvn -Plive -Dtest.jclouds.keystone.credential-type=passwordCredentials -Dtest.rackspace-clouddns.identity=username -Dtest.rackspace-clouddns.credential=password clean install

I probably won't be able to get to any review comments tonight. I'm busy prepping for giving two jclouds workshops tomorrow. Hopefully I'll be able to get to it ASAP and we can wrap this up before you head out on vacation. And if not...c'est la vie!