x/ref: jni cgo bridge for Invite Scan and Neighborhood Ad/Scan

Implements the jni layer on top of cgo.
We expose hooks to Invite Scan and Neighborhood Ad/Scan as well
as the corresponding Stop functions.

This wasn't perfectly tested, but I know that
- It compiles.
- TODOs app compiles with these changes and will at least get to the
  main screen. It will crash on watch and skips the login attempt.

MultiPart: 2/2
Change-Id: I0ca2173cee5f4e6820327d5862727577725c2831
9 files changed