Add empty unittest for factorization.
Work in progress on factorization algorithm.
Work on factorization algorithm.

Seems to work satisfactory for some basic set of expressions
in unit tests. Still need to integrate with compiler and test
in more complex situations.
Move unused geometry code out of the way.
Some work on cleaner language formatting.
Move geometry names class to uflacs.geometry.default_names.py.
Implement multidimensional array index mapping utilities.