Merge pull request #14577 from Rik/stop-ringtone-power-button-890434

Bug 890434 - Impossible to silence an incoming call without rejecting it r=etienne
Conflicts:
	apps/communications/dialer/test/unit/calls_handler_test.js
Bug 991666 - Fix removal of old API notifications when selected from the toaster r=alive
Merge remote-tracking branch 'upstream/v1.3' into mergin-1.3-in-1.3t-april-18

Conflicts:
	apps/callscreen/js/calls_handler.js
	apps/callscreen/test/unit/calls_handler_test.js
Merge pull request #18451 from etiennesegonzac/mergin-1.3-in-1.3t-april-18

Mergin 1.3 in 1.3t april 18