Support custom numbering style for different assets

[opoudjis]

Follow-on from #228

The additional requirement stated for custom numbering of notes, examples, requirements, formulas, term notes, term examples, annexes, admonitions, ordered lists (as distinct from list items), definition lists, figures, subfigures, tables, could be satisfied in one of two ways:

• Blanket Japanese numbering of all of them. That is not what the PDF document is doing, and without a written statement from a Japanese client saying that is what they want, I will not implement it, and the assumption that we can ignore what agencies have * actually done in their editorial practice is unacceptable.
• Customisation of all fourteen classes of counter, because we never know which preference any particular agency is going to go with, and we have no reason to think there is any consistency between them.

The second approach is the only respectful way to engage with customers. It is also 200-300 lines of code for what is, at this stage, a proof of concept that nobody external has actually asked for, and that no external agency is exercising QA over.

It is therefore not going to be a priority for me to work on until some agency actually does ask for it, and can articulate authoritatively how whether they want each of their notes, examples, requirements, formulas, term notes, term examples, annexes, admonitions, ordered lists (as distinct from list items), definition lists, figures, subfigures, tables to be numbered Japanese or Arabic.