Add units to framerate and gps data

Summary:
Add units to some of the properties
of kfilemetadata. This will mostly
be useful for baloo-widgets once
they are ported.

Reviewers: ngraham, bruns

Reviewed By: ngraham

Subscribers: kde-frameworks-devel, Baloo

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D18911