Adding support for default UI themes.
Merge branch 'next' of https://github.com/sgrenier/GamePlay into next

Conflicts:
	gameplay/src/Button.cpp
	gameplay/src/Button.h
	gameplay/src/CheckBox.cpp
	gameplay/src/CheckBox.h
	gameplay/src/Container.cpp
	gameplay/src/Container.h
	gameplay/src/ControlFactory.h
	gameplay/src/ImageControl.cpp
	gameplay/src/ImageControl.h
	gameplay/src/Joystick.cpp
	gameplay/src/Joystick.h
	gameplay/src/Label.cpp
	gameplay/src/Label.h
	gameplay/src/RadioButton.cpp
	gameplay/src/RadioButton.h
	gameplay/src/Slider.cpp
	gameplay/src/Slider.h
	gameplay/src/TextBox.cpp
	gameplay/src/TextBox.h