Airplane mode improvements

Summary:

• make the airplane mode to persist reboot/suspend or plasma restart
• make the airplane mode to disable/enable BT devices
• make the airplane mode hidden when there is no Wireless or Wwan device

BUG: 399993
BUG: 400535
BUG: 405447

Reviewers: Plasma, apol

Reviewed By: apol

Subscribers: ngraham, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D22680