feat: several improvements and fixes

- NiftyStatistics keeps track of FPS
- requestRedraw for Label methods that change attributes
- remember calculated minSize constraint to overwrite them again
- AbsoluteLayout now requires width or height constraint to be set
- RenderNode allocates new RTT if the dimensions changed
- RenderNodeSync will now skip nodes with width and height 0
- added demo FPS to UseCase_b10_CanvasProgressSpinner