custom camera controls implementation

[rob2d]

Relying on using OrbitControls just to be pragmatic to start, but this is far too limited along with other ThreeJS solutions so far (not to discount the possibility of using them); ideally there should be a camera with simple pan/zoom/rotation controls that do not bound viewable area.

MVP of custom implementation should strive to support:

• mouse controls:
  • move: rotate
  • + hold shift: pan
  • + hold control: zoom
• touchscreen/pad controls with two fingers:
  • + move: rotate
  • + pinch/expand: control zoom

Some consideration should be given to making sure that things are smooth (so no linear movement e.g. Math trig fns) + it should be easy to add controls for sensitivity later on.

[rob2d]

Users have not had significant usability issues with built-in OrbitalControls after adding a splash screen with hints on usage.

Would still be nice for several other reasons (e. g. programmatic camera for videos) but because of more interesting/functional features that can be added, marked this down to low-priority.