push gui code into GUI class...SDL2 system interface now handles

input for the most part..
create a somewhat hacky settings class, but it's better than

a bunch of statics in Game class.

handle mouse presses for sdl2..and convert those integers
implement sdl2 mouse wheel rocket handling
showcase of event handling for librocket
make the titlebar div instead of span
center titlebar, change titlebar icon..make it span the whole width

remove titlebar icon for now, maybe we'll use that some other year.

now there's just a slight 2 or 3px offset on the titlebar to the right
that's really bugging me..