Add DrawRectangle and use it to draw control borders
Add ability to specify background color for controls
Add support for docking controls to the edge of parent
Support displaying the mouse cursor
Mouse handling in UI and button control. Autosize textbox is now constrained by the parent width
Pass gametime down into UI draw
Add class for simple timer based animation
Add method to draw quadrilateral sprites. Bypass the sprite scaling stuff by passing the destination rectangle through to monogame directly.
Merge branch 'master' of https://github.com/Azathotep/LiteEngine