Allow to rotate viewports individually

[philippotto]

Detailed Description

The orthogonal mode always renders the planes axis-oriented at the moment. In the arbitrary mode, the user can rotate the viewport, but there is only one. The user should be able to rotate the viewports in the default "ortho" view (~could need some renaming then~ name would be alright as long as the viewports are orthogonal to each other).

Todo

• [ ] adapt bucket picking (reuse picker for arbitrary mode)
• [ ] adapt shader
• [ ] adapt mouse interactions
  • [ ] mapping of mouse position to voxel position
  • [ ] ...
• [ ] disable or support rendering of segmentation data in rotated viewport (how to interpolate?)
• [ ] disable or support volume tools
• [ ] UI
  • [ ] expose rotation value
  • [ ] ~allow "synced" mode where the rotation of one viewport, rotates the other viewports, too, so that the angles between them stay constant~ always keep viewports orthogonal to each other
  • [ ] "warn" user when angles are not axis aligned

Context

• [ ] Specific to long-running jobs (set jobsEnabled=true in application.conf)
• [ ] Specific to webknossos.org (set isDemoInstance=true in application.conf)

[normanrz]

I don't think the viewports should be rotateable individually but rather always stay orthogonal to each other.

[philippotto]

Great, then we can keep the name "orthogonal" mode for now.