Improve performance of matrix math.

Fix typo in vxnormalize
Add matrix generators

Generalise vector factories.
Allows us to reuse them as matrix factories.

Simplify vec/matrix ops

Fix lookups and add transpose

Change matrix constructor to row-major

Re-add inverse functions. Remove vec to-str.

Our custom vector toString method can be emulated with pr-str.

Revert the vector-of usage to plain vectors.

Despite the suggestive performance gains using vector-of,
it's actually horribly slow. Also expand out the
matrix inverse coefficients for a small win.