Api change/use entity proxies

Looking for early feedback on this.

My tests are working, and it all seems backwards compatible so far (but with ugly code in LocalManagementContext etc that I suggest we tackle in 0.6 when we delete more stuff?).

I've ported TomcatServer to the new format (i.e. interface+impl), but have not done the rest of the stuff yet.

When I start renaming classes to Impl and adding interfaces, it's going to touch almost everything! So am thinking that could be a subsequent pull request once folk are happy with the approach?

I'm also thinking we'll just break backwards compatibility with the renaming (e.g. if anyone out there references TomcatServer then it will no longer work until they update to say TomcatServerImpl or port their code to use the new way. Anything else seems like an infeasible amounts of pain and bad naming!