Pass NodeRenderer by value and move it
Call doDisableState instead of popping a renderer
Move definition of NodeRenderer to own file

This allows usage of NodeRenderer in other files without the need to include
FrameContext.h.
Use Util::Registry to register NodeRenderer

- Store Util::Registry as rendering channel in FrameContext
- FrameContext: Rename pushNodeRenderer to registerNodeRenderer
- FrameContext: Rename popNodeRenderer to unregisterNodeRenderer
- FrameContext: Require a handle for unregisterNodeRenderer
- Add new class NodeRendererRegistrationHolder that cares for automatic
  cancelation of the registration on destruction
- Store and use a NodeRendererRegistrationHolder in NodeRendererState
Use lambda functions for default renderers