Shorten AUTODOC_XML_HEADER, remove trailing whitespace in it
Improve Create{Main,Title}Page
CreateTitlePage: Introduce OutWithTag() to improve output

Readability (= "nice looks") of the generated XML seems important for
marketing reasons if we want to encourage use of AutoDoc for creating
documentation.
CreateTitlePage: also show maintainers

Perhaps this should be configurable, or perhaps maintainers should be
marked as such, but they definitely should be mentioned.
Create{Title,Main}Page: Some TODO comments
misc: reduce some minor code duplication
Merge branch 'create-page' of github.com:fingolfin/AutoDoc

* 'create-page' of github.com:fingolfin/AutoDoc:
  misc: reduce some minor code duplication
  Create{Title,Main}Page: Some TODO comments
  CreateTitlePage: also show maintainers
  CreateTitlePage: Introduce OutWithTag() to improve output
  Improve Create{Main,Title}Page
  Shorten AUTODOC_XML_HEADER, remove trailing whitespace in it