Bug 880628 - [MMS/SMS] Multi-recipient. Allow manual entry of duplicate recipients r=gnarf

https://bugzilla.mozilla.org/show_bug.cgi?id=880628
Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
(cherry picked from commit 4ff9f94fdc607209bf57b4843a8102229db147e7)

Conflicts:

	apps/sms/js/thread_ui.js
	apps/sms/test/unit/thread_ui_test.js

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>