Now With Broken Intro and Submenus!

Added in the submenu for Unit management, as my first benchmark is to be
able to create and edit units from the UI.
Basic code fixes.
Added a new intro movie made with After Effects, currently breaks due to
MPEG-1 file limitations, will try to find a workaround, hopefully using
something not MPEG-1 related. Might have to stray from Pygame for that
though, as the Movie class is horridly outdated.