cmsdk: Add CMSettings preference helpers

 * These lived in the Settings app previously, but are now moved as
   we need them in a few places.
 * The support library required to use these helpers, but we
   intentionally reference it using LOCAL_JAVA_LIBRARIES so the
   application will need to declare a dependency.

Change-Id: I56844def5e1100ca0300d0027312cc9adcaab941