Annexes to list non-normative comments, such as usual limitations on lighting

Bart Hanssens suggests for dr3d:light where we note that a typical limitation is eight lights, that it might be useful to gather up the non-normative comments for say lighting in an annex.

He made the comment in the context of reviewing 1.2 but I don't want to lose it for ODF-Next. Could be an interoperability point to document common implementation practice. http://lists.oasis-open.org/archives/office-comment/200812/msg00017.html