[SDL Widget] Rename 'SdlWidgetBase' to just 'SdlWidget'.
[SDL Manager] Move widget count update to top of update() instead of expecting every create* method to update it.
[SDL Utility] Implement new SDL Utility class for creating surfaces and SDL_Rects.
[SDL Widget] Add 'WIDGET_DISABLED' state. Add 'moveTo()' method.
[SDL Manager] Add general 'addWidget()' method to add widgets to the draw-list from outside of the 'create*' methods.
[SDL Manager] Move 'renderWidget' to different area of implementation file.

Move this method closer to the 'update()' method where it is called.
[SDL Utility] Add 'getColor()' method.
[SDL Utility] Change usage of 'Surface *' to 'ImageReference'.
[Game Manager] Fix typo on 'showCreditsButton'. Disable 'New Game' and 'Show Credits' buttons.
[SDL Button] Move default button creation out of Manager and into the Button class.
[SDL Entity] Implement SDL Entity class.

This class should be manager externally by a object which understand the Mobile Entity class.
[SDL Triangle Slider] Implement Triangle Slider widget.
[SDL Utility] Rename 'makeRect()' to 'createRect()'. Implement 'createTriangle()'. [SDL Widget] Make 'isInside()' virtual.
[main] Implement Triangle Slider Demo.