fix Qt connection in ScalarToColorMapping

replace lambda target with member function, so that the connection will automatically get deleted if the mapping dies
RenderView is now completely independent from rendering implementation

- introduce base class AbstractVisualizedData for any kind of rendered/plotted data
- move ScalarToColorMapping from RenderView to RenderViewImplementation3D, as it is currently only implemented for 3D rendering scenes
- rename all *renderedData* to *content* in RenderView
rename RenderViewSwitch -> RenderViewStrategySwitch
add RendererImplementationSwitch, move RenderViewStrategy into RendererImplementation3D
fix some events/assertions
use Context View for profile plots