Refs #10364 Merge Refl presenters into ReflMainViewPresenter
Refs #10364 Add unit tests for ReflMainViewPresenter

These unit tests are by no means complete, and are due for a complete
overhaul in the near future. They do however cover almost all
functionality, so they are sufficient for the moment.
Refs #10364 Remove ReflMainView.cpp
Refs #10364 Move instrument list logic out of ReflMainView

The presenter is now responsible for giving the view a list of valid
instruments and selecting a default one.
Refs #10364 Test loading invalid workspaces

The old tests were dropped during the merge. Let's re-add them.
Merge branch 'feature/10364_merge_refl_presenters' into develop