We now try to open image files dropped on us from FileManager. :^)
The QuickShow code is not exactly well-factored, and should be fixes up
to not do the same thing twice, etc.
This behavior and API was extremely counter-intuitive since our default
behavior was for applications to never exit after you close all of their
windows.
Now that we exit the event loop by default when the very last GWindow is
deleted, we don't have to worry about this.
Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.
This avoids building the code twice, and will encourage better separation
of concerns. :^)
This needs more work and polish, but it's a step in a more pleasant and
useful direction.
Also turn QuickShow into a fully-fledged "application". (By that, I really
just mean giving it its own Applications/ subdirectory.)
