Update the libraries test.

- 'update' now takes a library object, not a string - because the string
  might be xml or json.
- Categories are stored in alphabetical order.
Fix name of BoostVersion
Scrape maintainers from repo.

Should probably actually do this in create-module-metadata, as once the
metadata is in place this script should ignore the maintainers file. But
I didn't have much time tonight. So I won't check the changes into
libraries.xml. Also need to consider that 'maintainers' should probably
be backdated to apply to all versions. Maybe it shouldn't be store in
libraries.xml at all.