This allows running DMDirc from IDEA, which seems useful.

Running a normal build just replaces the file in the build output.

At present anything requesting the global config has to depend on
ClientModule, which won't necessarily be exposed through the API.

Move @GlobalConfig, @AddonConfig and @UserConfig to top level
classes in API, and provide both versions of them for now.

Stop swimming against the tide and accept what most of the rest of
the world does.

While it adds an annoying depth to the actual source code, it makes
the root directory nicer (no more 'test-res' dirs), means we don't
have to override the gradle config, and makes it nicer to work in
IDEA 2016.1.