Mms: Send message to multiple recipients

Add a function that user can send message to multiple recipients.
It allows user pick multiple recipients from contacts and
send message to them at the same time.

Change-Id: I23503e4a1454d501153884e61bc39b259d8030ed

Conflicts:
	res/layout/recipients_editor.xml
	res/values/strings.xml
	src/com/android/mms/ui/ComposeMessageActivity.java