Feature request: new kind of Subgroup Lattice visualization

[nathancarter]

Right now GE supports subgroup lattice visualization using sheets, with each vertex in the lattice being a subgroup represented by a visualizer (MT, CD, or CG). But in Visual Group Theory, there are several illustrations that show subgroup lattices with the subgroups represented just by the generators for that subgroup, as in the image shown below.

This should be pretty easy to replicate in GE by upgrading the lattice-creating code so that it uses sheet TextElements instead of visualizers, and just places the appropriate text in them. This probably requires upgrading TextElement to support math, but it may already do so.