Implement syncing of theme preferences between SDDM and Plasma
This patch exposes UI options in sddm-kcm which enable users to sync their theme preferences used in Plasma with SDDM.
Syncing of UI font, font rendering, color scheme, desktop and icon theme has been implemented.
A reset button has also been added in order to allow easy removal of all SDDM syncing-related customization.
For testing a different font, you need to have a file like this one:
Reviewed By: ngraham, VDG
Subscribers: leinir, cfeck, GB_2, ndavis, plasma-devel
Differential Revision: https://phabricator.kde.org/D22191