Factorization systems

Of course, this is preliminary to constructing the connected/truncated factorization system for any modality.

This file is twice as slow to compile as the previously slowest file (namely `V.v`).  Adding explicit universe annotations sped it up by a couple of seconds already.  Any other suggestions would be welcome.
Hmm, I guess so.

Unrelatedly, I've been thinking that the numbers on the issig tactics are off by one.