Bug 990003 - Introducing a dedicated callscreen app for dramatically
improved performances.

(cherry picked from commit 6513fe73854d7743e66eb3f1cfbbdf4e04874c3f)

Conflicts:
	apps/callscreen/index.html
	apps/callscreen/js/call_screen.js
	apps/callscreen/js/calls_handler.js
	apps/callscreen/style/images/ActionIcon_40x40_audiosourcemenu.png
	apps/callscreen/style/images/ActionIcon_40x40_audiosourcemenu@1.5x.png
	apps/callscreen/style/images/ActionIcon_40x40_audiosourcemenu@2x.png
	apps/callscreen/style/images/picture_emergency.png
	apps/callscreen/style/images/picture_emergency@1.5x.png
	apps/callscreen/style/images/picture_emergency@2x.png
	apps/callscreen/test/unit/call_screen_test.js
	apps/callscreen/test/unit/calls_handler_test.js
	apps/callscreen/test/unit/conference_group_handler_test.js
	apps/callscreen/test/unit/handled_call_test.js
	apps/communications/dialer/index.html
	apps/communications/dialer/js/call_log.js
	apps/communications/dialer/js/dialer.js
	apps/communications/dialer/test/unit/call_log_db_test.js
	apps/communications/dialer/test/unit/call_log_test.js
	apps/communications/dialer/test/unit/dialer_test.js
	apps/communications/dialer/test/unit/keypad_test.js
	apps/communications/dialer/test/unit/multi_sim_action_button_test.js
	apps/communications/dialer/test/unit/phone_action_menu_test.js
	apps/communications/dialer/test/unit/sim_picker_test.js
	apps/communications/dialer/test/unit/suggestion_bar_test.js
	apps/communications/dialer/test/unit/telephony_helper_test.js
	apps/system/js/attention_screen.js
	apps/system/js/bootstrap.js
	apps/system/js/dialer_agent.js
	apps/system/style/attention_screen.css
	apps/system/test/unit/bootstrap_test.js
	build/csslint/xfail.list
	build/jshint/xfail.list
	build/webapp-zip.js
	shared/style/dialer/keypad.css
	shared/test/unit/mocks/mock_navigator_moz_telephony.js
Merge pull request #18294 from etiennesegonzac/instacallscreen-v1.3t

Bug 990003 - Introducing a dedicated callscreen app for dramatically