This layout is intended to replace the TabBox mode in Present
Windows effect.
The advantages of a layout over the effect are:
* works without compositing
* supports multi-screen in a better way (windows don't move)
* is an overlay on top of the windows instead of reusing the windows
* is not a hack inside the actual effect
* visually consistent with other layouts
A new service type is introduced which is used by the KCM to find
all available window switcher layouts. This makes it finally possible
to have 3rd party window switchers.
Also the tabbox finds the packaged QML file through the service
definitions.
Desktop switcher is not yet in packaged version (UI to configure
is missing).
REVIEW: 103951