Support uniform honeycombs

[roice3]

i.e. support any set of active mirrors in the Coxeter diagram. Right now, we're mainly supporting mirror 1 being active, and kind of supporting mirrors 1 and 2 being active with the "truncations".

This task depends on first extending the support for symmetry groups: #3

An important part of this will be to pick a good UI. Maybe 4 checkboxes for the active mirrors?

[henryseg]

Currently all scenes have the full symmetry of the cube. So we could use all mirrors for all scenes, at a minor processing cost. Are you suggesting scenes with less symmetry?

[roice3]

Sorry this wasn't clear. I edited the title and changed the wording a little (also fixing a mistake I had written). By "active", I mean in the sense of which nodes are marked with rings in the Coxeter diagram, as described here.

So I'm not suggesting scenes with less symmetry (that seems further off), but suggesting we support the up-to 15 possibilities for the uniform honeycombs that share a given symmetry group. This will be a pretty easy addition once we complete #3, as it is just about picking the right vertex point in the fundamental domain. Mirror planes will be active if they don't contain the vertex.

And of course, we could add more coolness after reaching that milestone, like alternations, duals to uniforms, etc.