Bug 960756 - Add CONFIG_MAX_SNAPSHOT_PIXEL_SIZE. r=djf

This allows configuration of the max resolution of camera snapshots
independently from the max resolution of displayed images.
Bug 959660 - [System] Prevent show/hide attention screen again when it's already hiding
Bug 957678 - Fix activityCaller/Callee ref in the chain
Bug_935991:[Messaging]Modified the Order of menu options and updated testcase a=fabrice

(cherry picked from commit 0c1a1c763a94c112094de944e1822df0f90455ba)

Conflicts:
	apps/sms/js/thread_ui.js
Merge pull request #15540 from SasikalaParuchuri/Bug_935991_Added_Test_For_Delete_Option

Bug 935991 - [Messages] Added new test for Delete menu option r=julienw
(cherry picked from commit 1c7d574e9fbf5d5cab8a001d50056460c733b638)

a=tests
Had to slightly change the tests compared to the master patch.
Merge pull request #14810 from etiennesegonzac/bug-946316-mochitest

Bug 946316 - Adding data store access to the mochitest app. r=etienne
Merge pull request #15622 from dwilsoncaf/bug-960756-v1.3

Bug 960756 - Add CONFIG_MAX_SNAPSHOT_PIXEL_SIZE. r=djf
Merge pull request #15594 from rexboy7/fix-bug959660-v1.3

Bug 959660 - [System] Prevent show/hide attention screen again when it's...
Merge pull request #15523 from timdream/window-activity-chain-v1.3

Bug 957678 - Fix activityCaller/Callee ref in the chain, r=alive
Bug 961047 - Remove some dead code in Gaia with APZC enabled by default from the platform. r=alive,fabrice