Because the usual content provider interface doesn't allow specification of
the target user under which to perform settings reads/writes, this CL introduces
a new command line app specifically for that.
Usage:
settings [--user num] get namespace key
settings [--user num] put namespace key value
If a --user argument is not given, the owner user is targetted.
Bug 7299066
Change-Id: I73108bb76b04fad133cc4e0f218d64490de549f1
