TEST: Add unit tests for Qt code

[cbertinato]

Using QTest, or something else.

[bradyzp]

Just making a note here on progress, and what's still left to be done.

Tested UI Components:

• [x] Most dialog forms
• [x] 90% of *_controller classes
• [x] New base plotting API

ToDo:

• [ ] Menu/actions defined within controller classes
• [x] Main Window
• [ ] Tab workspaces
• [ ] LineSelectPlot (based on the new plot API)
• [ ] Splash screen