First implementation of a widget window inside the scene
Merge branch 'SDL2' into OVERLAY

Conflicts:
	LISA/gui/sdl2/OGLWidget.py
	LISA/gui/sdl2/window.py
Changing the interface for events, had widgets manipulation and other stuff
Merge remote-tracking branch 'origin/testing' into textures

Conflicts:
	LISA/examples/rippler/rippler.py
	LISA/gui/sdl2/OGLWidget.py
Add a texture manager and widgets
Merge pull request #10 from Acanthostega/textures

Textures and widget