Further improvements to OCG apparmor profile.

* Allow OCG to read default papersize.
* Allow rsvg-convert to read mime type database.
* Allow imagetools to read their own binaries.
* Allow imagetools and xetex to write to postmortems.

Change-Id: Id23b7ac9dd1cd782d6172de89052b299fb897707
Merge "Further improvements to OCG apparmor profile." into production