WIP Lockscreen notifications

This adds initial lockscreen notification support. Clicking the notification gets one to the unlock screen and activates the appplication after unlock. We hide body and actions atm since that's the default on the lockscreen per GSettings. It's a property already though so easy to toggle on. Global "show-in-lockscreen" gsetting is also handled for privacy concerned people.

A bit hard to review since it's on top of next. I'll unwip once the needed baseline is in.

Signed-off-by: Guido Günther guido.gunther@puri.sm