Expand number variables to match locator types

[badumont]

It is possible to refer to a wide variety of locator types in a citation, but in the bibliography we are stuck with page, volume, chapter-number, part-number and section (in 1.0.2). In History, I can find at least two frequent cases where it is problematic:

• An item in a manuscript (where we count with folios, not with pages): Procopius Gazaeus, Letters, Marc. gr. Z. 521, ff. 109v-111;
• An opus or an article in a volume that has no pages, but columns: John Chrysostom, Homily 64 on John, Patrologia graeca 59, cols. 353‑360.

Would it be possible to create one number variable for each locator type to allow for their use also in bibliography?

[bwiernik]

This is being done all as part of the page variable in CSL 1.1, with the same structure as locator.