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:

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

ToDo:

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