Add client interaction functionality

[tdaffin]

I'm not sure if this is the kind of thing you want to do with this tool, but I find it really useful to be able to keep the test world open when testing is over, and then connect to it with a client and take a look around to see if the world looks the way I expect it should given the tests that I've run.

To this end I've added the following features:

• Added a shutdownOnEndTesting flag so that the server can be kept running when testing ends
  Setting this flag on causes the server gui to be shown so that the user can manually save and/or stop the world
• Switched off world auto save by default so that nothing will ever get saved automatially
• Allow a client that does not have Barometer installed connect to the world
• Added an 'exit' command so that the server can be manually stopped in the same way it is normally stopped after testing -- guaranteeing that nothing gets saved. The user still has the option to use the regular 'stop' command to save the world on exit.

[jjtParadox]

I like this idea, but I think this should be separate from the usual gralde test command to prevent people from accidentally throwing away CI minutes by leaving the server running.

Could this instead be made into a server command that runs the tests in an already running environment?

[tdaffin]

I see what you mean. I like the idea of using server commands to control the testing as well -- it might also be possible to add commands to run just one test at a time and so forth.
I'll look into the simplest re-implementation of this as commands first, and then perhaps look into additional commands in subsequent pull requests.