Rewrite the taglib extractor to use the generic PropertyMap interface
Rewrite the taglib extractor to use taglib's
PropertyMap. Since this largely unifies the handling of the
different tag formats, but not quite, a lot of code is removed.
The resulting code is also faster. Additionally, this avoids the
usage of a FileRef object, which fixes a potential crash due to
a known bug in taglib.
Test Plan: all tests pass
Reviewers: ngraham, bruns, mgallien
Reviewed By: bruns
Subscribers: smithjd, kde-frameworks-devel, Baloo
Differential Revision: https://phabricator.kde.org/D18826