Generate resource module (for displaying images)

- Use pyrcc4 for generating a python module (ui/images_rc.py) from a Qt
  resource file (.qrc) to allow resources, such as images, to be loaded
  from disk
  - Command: pyrcc4 -py3 -o ui/images_rc.py ui/resources/images.qrc
  - Note: This file will need to be regenerated as resources are added
- Import resource module in main.py
- Test images displaying in app (command buttons have test image)
- Note: Any developer using PyCharm must mark the ui directory (not
  src/ui, that should be all set) as a "Sources Root" to allow the rc.py
  file to be imported