Refactor TestProjectController and TestProject to be closer to reality.

This allows us to purge DummyProject and centralize some code. Furthermore
the TestProjectController now no longer sets up a BuildSetModel since
we do not want to test that anyways.

Finally, and this was the main intention, we can now rebase the QuickOpen
unit test to operate on the actual ProjectFileItem* like it would do
in reality. This hopefully allows me to test some optimization ideas I have.

Note: I've also cleaned up some CMakeLists.txt files while at it.