MMS: Add support for query memory usage of the terminal

Query memory usage of the terminal, including:
1. Counts of messages in index/sent/outbox/drafts.
2. Used/unused space by MMS and total space in phone.

Change-Id: I35eaf13ee3b9014738a69490a6687215e3c434ea
(cherry picked from commit 4249b13ad53f6ef51f892505bfb299fa9edc4da1)

Conflicts:
	res/values-zh-rCN/strings.xml