New recommendations topic: document structure and versioning

[Klortho]

This topic needs to cover things like:

• Checking for the processing instruction that self-identifies this document (see issue #10)
• Checking for a doctype declaration, and that it has a recognized public identifier - this can't be done in schematron, but can be part of the preprocessing that handles the DTD (see issue #49)

It came up at jats-con, that we'll need to add some metadata to various rules (scope) such that, for example, checks that ALI tags are used only apply to documents > 1.1d3 (see issue #50).

[Klortho]

This should probably be merged into the same topic as the draft JATS4R schema processing instruction recommendation. It should also include things like the doctype declaration, use of public and system identifiers, if we want to address those.

I'm not sure what a nice, concise name for this topic might be. How about "xml-document-rules".

[Klortho]

I renamed "filenaming" -> "general-recommendations", and merged a couple of other issues into this category, as described above.