GitLab

This ports the widget style KCM to use a grid view KCM with live preview thumbnails and inline configure button.

* Icon and tool bar settings have been moved into a popup, similar to Icons KCM, to leave more room for the rather large thumbnails
* Overall cleanup of unused/defunct features and modernized codebase
* Support for non-Linux is dropped, i.e. it assumes "Breeze" as the default, no "native" (e.g. Mac or Windows style) as we want
  our apps to follow whatever other platform they run in, rather than offering this KCM there

Differential Revision: https://phabricator.kde.org/D24361

This is the beginning of revision history for this module. If you
want to look at revision history older than this, please refer to the
techbase wiki for how to use Git history grafting. At the time of
writing, this wiki is located here:

http://community.kde.org/Frameworks/GitOldHistory

If you have already performed the grafting and you don't see any
history beyond this commit, try running "git log" with the "--follow"
argument.

Branched from the monolithic repo kde-workspace, frameworks  branch, at commit
049113e719dd2fc4446d054fa1a3aada330094f0