Allow viewing of RGT files
Debugging aid: Destroy the main window on application exit.
Debugging aid: Allow D2D and DWrite to be disabled.

The Visual Studio graphics debugger doesn't like D3D10 being used alongside these technologies.
Allow viewing of PNG files
Allow mouse dragging of scrollable windows
Fix BC1 loading bug.
Support loading 24-bpp TGA files
Allow viewing of TGA files