Removal of all unported/unbuilt applets, dataengines, runners, wallpapers

Summary:
With no-one having invested into porting/maintaining any of those plugins,
the disadvantages of keeping that code in the development branches
(translators getting data of dead code, developers searching for usage
examples hitting lots of dead code, seeing all the unported plugins/
lost work making sad) are not worth it.

Besides, all the applets will need to be substantially rewritten from
C++ to QML anyway, so a direct code history will not be that useful.

R.I.P., dear code, thanks for all the services. And may you find some
development gods to help you into a reincarnation soon
(special thoughts to eyes and bubblemon applets).

        @}-,-`-

Reviewers: jriddell, mart, davidedmundson

Reviewed By: mart

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D10163