Structural alg traversal

[lgarron]

Many alg operations can be supported on "unflattened" algs (i.e. commutators and conjugates unexpanded).

• Move count.
• Total animation time (given time for each move token).
• Puzzle state at a given position.
  • See #46.
  • There's no reason we shouldn't be able to support algs with arbitrarily many moves (millions? trillions?), as long as the nested representation is concise.

It should be simple to write something to do this in general. It just requires something that can handle JSON traversal given handlers for the following nodes:

• basic moves
• groupings
• commutators
• conjugates

[lgarron]

This is implemented in alg.cube.makeAlgTraversal()