JDF-409: Replace richafaces quickstarts by a git submodule

Removed the kitchensink-rf and helloworld-rf quickstarts, and added the richfaces quickstarts repository as a submodule.

This PR is first done without a richfaces tag in the submodule, pending a review by the JDF team.  Once we have agreed that everything is ready to merge, I will update the PR pointing the RichFaces git submodule to a tag.