Closes #751

The styliser needs an interface extracting into the API, and
we don't really want huge static methods defined on that.

Mockito now errors if a mock is unnecessary, plus a few other minor
API changes.

Some other minor tidying to Styliser.

This is just an IntelliJ refactor, using EventBus in place of
DMDircMBassador whenever possible.

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.