Allow range formatting for all numbers (esp. dates)

The page-range-format attribute only applies to page numbers (as one would expect), but style guides typically extend these rules to all numbers. This is most notably an issue with date ranges; for example, the following citation (using Chicago author-date) is currently impossible to achieve with CSL:

Karenberg, Axel. 2012–13. ‘The World of Gods and the Body of Man: Mythological Origins of Modern Anatomical Terms’. Anatomy 6–7: 7–22. doi:10.2399/ana.11.142.

I originally proposed on xbiblio-devel to simply extend the page-range-format attribute to all numbers, but @rmzelle noted the following:

My gut feeling is that it’s better to have separate definitions of range formatting for dates and all other numbers, so that they can be configured separately. Volume, issue, and series number ranges don’t come up very often (in practice and in citation manuals), so we haven’t really thought about whether the page-range-format should affect them.

This is an issue, for example, in the OUP House Style, where dates use a different formatting scheme from other numbers.

[bwiernik]

Seems like more than a delimiter issue, but rather a whole collapse-year-range formatting question? Compared to the cite collapsing within author and year?

[bwiernik]

I think that page-range-delimiter can probably apply to volume ranges, issue ranges, etc. (so number ranges generally). Date ranges should have their own delimiter as suggested.