Fix error while loading theme_reference.svgz

While loading the standard theme in parley the following message was
shown on stderr:

Could not add child element to parent element because the types are
incorrect.

This message came from QSvgRenderer while loading theme_reference.svgz.
The svg file was malformed. The faulty text field was deleted and
rebuild. Additionaly the Bitstream Vera Sans font was replaced by
a standard sans font.

Download links for reference files were updated to git repos.
Path for theme location was updated to KDE5.

REVIEW: 127321