numbers.py: Precision; fix spelling, remove hard line-wrap and make
            render in LaTeX better
symbols.py: Need \n after </dl>. Hash was not doctest'd properly
combinatorial.py: Add Subset link; shorten Subset test output,
constants.py: better Infinity exmaples, link to DirectedInfinity
orderstats. WMA -> WMA link (when there are no other links)
expression_tests.py: move and *Q here.
systemsymbols: More symbols

we don't know how to install WordCloud on Windows without it giving

ImportError: DLL load failed while importing _c_internal_utils: The
specified module could not be found.
(from matplotlib)

on Expressions

Add another "\n" at the end of a </dl>

Compute number boxwidth automatically in tocbox numbers