Use a separate kernel config for CM10.2 builds

It's possible to have a single kernel image for both CM10.1 and CM10.2,
but that would impose an ABI change on CM10.1 builds.  Let's keep the
10.2 config separate, at least for now.

Change-Id: I46272f3de25dd87528b9057f9ae55353058cd745
Update build fingerprint to match razor (Nexus 7 2013) JSS15J

CM10.2 is currently based on the JSS branch (jb-mr2.0-release), not the
JWR branch (jb-mr2-release), so it's more correct to report JSS15J as
the build ID instead of JWR66V.

Change-Id: Ieb4e049e41286d5cc1b241e59e34674646dd753b