Removed libraries + GUI changes

Removed C libraries, will need to notify the end-user to include them
though.
Renamed GUITools to GUI (along with the namespace).
Split button into a basetype (TextButton) for inheriting from, and the
actual button object.
Added FullImageButton.
Set up the same split thingy for VerticalScrollbar and
HorizontalScrollbar with a base Scrollbar class (only VerticalScrollbar
functions for now though). #115
Renamed LogicalObject to GameObject.