Settings: add back SMS security limit

Limit the number of outgoing messages per every 15 minutes by
any application that sends text messages.

PS2-4: Whitespace fixes

Change-Id: Ibb61396ea9adb3f95cdbd13b91cbbc3477f6e361
Update the SMS sending limit instantly (2/2)

This commit also shortens and simplifies the preference summary text
considerably.

Patch set 2  : Slight rewording
Patch set 3  : Another minor wording change

Conflicts:
	res/values/strings.xml

Change-Id: I75394ee92fa5d85c84fa0bc32f5037afe6a8a3cd
Merge branch 'cm-11.0' into martincz