* Implemented GuiResizableControl, and made GuiWindowControl inherit from it.
GuiResizableControl is a control that can be resized.
GuiResizableControl calls SetCursorForResize(_resizingSides), which can be overriden to provide platform specific mouse cursor implementation depending on where on the edge of the control your mouse is.
* Screen Desktop defaulted to being width of 1, and height of 1, instead of width of 100%, and height of 100%
* Including class reference in project
* Implemented Size3 and Point3. Fixed bug in Point2. Documentation listed Point2, but code took in Vector2. Changed to Point2
* Adding missed project references
* Fixed assert errors: https://github.com/craftworkgames/MonoGame.Extended/issues/474
* Fix merge issue
Dylan Wilson