Make tabular numbers & currencies; make proportional number feature

[arrowtype]

The fonts have some tabular characters, to make data tables, pricing labels, etc easier to design. Tabular glyphs include:

• numbers
• arrows
• currencies

Remaining tasks:

• make dollar match tabular number width, 700
• swap non-split-bar dollar with split one
• make proportional figures, completely-simple one.pnum
  • kern, if necessary?
  • research: should anything else be tabular or have a tabular alternate? what would it take to add these into the build-prep...?

[arrowtype]

These so far don’t have alternates to cycle through, but this might be something worth adding at a later point. To do so, prep-build.py would have to be modified to handle glyphs with suffixes, which it currently doesn’t.