ENH: Added performance related options to GPU volume rendering
- Added option to use the mapper's feature LockSampleDistanceToInputSpacing to calculate it internally instead of setting sampling distance manually. Off by default. This applies only for GPU rendering. If it's on, then AutoAdjustSampleDistances is disabled, because it prevents using this feature. Because of this, if the flag is on, then the MaximumQuality and AdaptiveQuality setting does not work
- Added UseJittering option to GPU display node. If turned on, then uses random noise to remove the wood-grain artifact. Off by default. Not exposed on the UI yet
- Widened range of FPS slider for adaptive mode to accommodate for new virtual reality use cases (maximum used to be 20, now it is 100)
- Removed empty "Misc" tab from Volume rendering module UI
- Fixed ctkDoubleSlider related warning message
- Modernized vtkMRMLVolumeRenderingDisplayNode to use node references and new property macros. This fixed several bugs as well (e.g. not reading/writing attributes)