Bug 941030 - Merge pull request #14653 from fcampo/mms-forward-subject-941030

Bug 941030 - [Messages] Follow up Bug 919966 - Ensure that forwarding a MMS with a subject fills in the subject in the composer
(cherry picked from commit 4df4a5b17839fc6ce748029fc1e79bb2bde3cc87)

Conflicts:
	apps/sms/js/compose.js
	apps/sms/js/message_manager.js
	apps/sms/test/unit/compose_test.js
	apps/sms/test/unit/mock_compose.js
        apps/sms/test/unit/message_manager_test.js