Code review comment for lp:~leonardr/lazr.restful/test-multiversion-collection

This branch changes the multiversion.txt doctest so that there are two different implementations of the 'contact' collection; one used in the 'beta' and '1.0' versions, one used in the 'dev' version. There is no new code; the test merely illustrates something that was already possible.

I also changed the overly long names of the marker interfaces used to designate different versions of the web service. IWebServiceRequestBeta now becomes simply IBetaVersion, and so on.