Fix the tag 'size' when viewing a profile in cd-iccdump with newer lcms versions

Newer versions of lcms2 don't have the bug where they read the whole tag out,
and now returns the size of the read (a good thing!).
libcolord: Add functionality to read and write raw tag data

Also add the 'export-tag-data' subcommand to cd-fix-profile. This will help
very much when debugging broken profiles and showing vendor secret sauce.