Volume rendering using XTK WIP.
Transfer the image volume as zipped raw bytes.
Transfer RAW data for images and segmentations properly.
WIP regarding XTK based Volume Rendering.
Re-activate the volume rendering of the labelmap.
Volume rendering works (without thresholding).

Also, fixed some bugs on the way.
Add compiled XTK with working volume rendering.
Show bounding box of the volume and a red slice indicator.
Move 3d slice indicator when scrolling through slices.
Better integrate the 3D rendering mode.
Use compiled XTK and also make the 3D window resizable.
Add the dragresize.js library.
Some picking experiments.
Improve the workflow in 3D mode and in merge mode when in comes to the 3D aiding.
Merge branch 'volume_rendering'