Provide Ability in Documentation Language to Change Appearance of Table of Symbols

[smiths]

The documentation language should allow the document designer to select the format of symbol tables to match their preferred style. Different options can be seen by comparing the table of symbols for the NoPCM example, in the manual version versus the stable version. (A similar issue #426 was created for the table of units.)

An example variability is the format of the units when there is division. Three obvious options include:

1. fractions, like the LaTeX frac statement
2. same line, using a slash /
3. negative powers, like kg^{-2}

Manual version

Stable version