implement flush seek on every frame when paused
refactor

* extract shaders from python code
* extract super class from CairoGLSink
* merge draw functions
* make new opengl objects, move to opengl file
* make actor class
* split actors into classes
* split actors and graphics
remove old box code. implement new box graphic
draw correct aspect ratio for box. clean up
refactor 2

* transformation is not optional
* move all rendering related code from sink to scene
* use scene functions in callbacks, rename handlegraphics class
* delete clutter stuff entirely
Make scene adapt to the sliders.

* Branch slider box classes
* calculate mvp matrix from element properties
add reset button. make sliderbox superclass