zDoom Launcher v2 Modern UI Overhaul

Additions

1. Many controls now have tool-tips.
2. Controls to change between light and dark themes and select the accent color.

Changes

1. Major overhaul of the UI structure with much functionality now moved to a command bar.
2. The program now has theme support and will adapt to OS theme on Windows 10.
3. An IWAD file can now be set to nothing to allow the selection dialog popup when starting zDoom.
4. Renamed "Game-Play Options" to "Gameplay Options".

Fixes

1. Cleaned up unnecessary files from the release package.
2. The launcher should now shutdown after closing the main window, even if there are more videos open.
3. Allow zDoom installation folder to be changed if the chosen one still exists.