Segmentations: Ensure FilterMode is set to FilterMode.Point on start/enable in

[mlavik1]

For segmentations, the FilterMode is set to FilterMode.Point in VolumeRenderedObjects.cs. However, this gets reset on load (if you load segmentations and then save the scene).

It may be better to create a separate VolumeDataset subclass or something for segmentations, or add some settings for this directly to VolumeDataset.

Note to self: Fix this before releasing segmentations.