ODF 1.2 part 1 cd03 - split 3.16 into subtitles

Hi,

Digital signatures are an important new feature, so IMHO it deserves
some more attention (including small layout changes, in the current
version it seems a bit crammed together into one section)


Suggestion to split 3.16 into

3.16 Intro

3.16.1 Document Signatures
...
3.16.2 Macro Signatures
...
3.16.3 Implementation specific
...


Best regards,

Bart