Bug 834530 - Make the TonePlayer handle the channel sounds will be played on r=drs

(cherry picked from commit 20a56c3cf6ea6b730d05d7a8cfa06e178cd5717c)

Conflicts:
        apps/callscreen/js/calls_handler.js
        apps/callscreen/js/index.js
        apps/callscreen/test/unit/calls_handler_test.js
        apps/communications/dialer/js/dialer.js
        apps/communications/dialer/js/dialer.js
        apps/communications/dialer/test/unit/keypad_test.js
        apps/communications/dialer/test/unit/tone_player_test.js
        apps/emergency-call/index.html
        apps/emergency-call/js/dialer.js
        apps/emergency-call/js/keypad.js
        apps/emergency-call/manifest.webapp
        apps/emergency-call/test/unit/keypad_test.js
        apps/sharedtest/test/unit/dialer/telephony_messages_test.js
        build/jshint/xfail.list
        shared/js/dialer/keypad.js
        shared/js/dialer/telephony_messages.js
        shared/js/dialer/tone_player.js
        shared/test/unit/mocks/dialer/mock_calls_handler.js
        shared/test/unit/mocks/mock_audio.js