This reverts commit 8da1d786.

plus:

Revert "Revert "KDE: don't throw on TemplatePathVariable""

This reverts commit 72812a38.

I had misread the code and thought that handling of those two properties in
shell/source/backends/desktopbe/desktopbackend.cxx would hide handling them in the
specific KDE backends, but that is not actually the case.

Change-Id: I32fae5ba34cc934ceca2f574d50fc327b506b001