Added ability to toggle enable/disable Send on Enter

Change-Id: Ic7cee9e5babc42d5c00ac50f7a490369b3a3d936

Conflicts:

	res/values-ja/strings.xml
	res/values/strings.xml
	res/xml/preferences.xml
	src/com/android/mms/ui/ComposeMessageActivity.java
	src/com/android/mms/ui/MessagingPreferenceActivity.java

ported from https://github.com/CyanogenMod/android_packages_apps_Mms/commit/c1c34810b3723a4e897d1c833057b17d3f6a0a05

Signed-off-by: rdgate <rdgate@gmail.com>
Merge commit 'refs/changes/87/7087/1' of http://gerrit.sudoservers.com/AOKP/packages_apps_Mms into jb-mr1