D25742: move backgroundhints managment in Applet

[Marco Martin]

mart added a reviewer: Plasma.

REPOSITORY
  R242 Plasma Framework (Library)

REVISION DETAIL
  https://phabricator.kde.org/D25742

To: mart, #plasma
Cc: kde-frameworks-devel, LeGast00n, GB_2, michaelh, ngraham, bruns