Integrate mobile service into ns-server build

When building Couchbase Server, it should build the mobile-service binary, which will eventually be spawned by ns-server after the integration is done.

The mobile-service is written in go, and the code lives here:

https://github.com/couchbase/mobile-service/

In terms of dependencies, it currently has the following third party golang deps:

• google.golang.org/grpc Package grpc implements an RPC system called gRPC.
• google.golang.org/grpc/reflection Package reflection implements server reflection service.

which will need to be mirrored in couchbasedeps.

What are the steps to integrate this into the Couchbase Server build process? I'm imagining that we'll at least need to do the following:

• Determine the manifest file – this is targeted for Couchbase MadHatter, so I assume that means branch-master.xml?
• Add a CMakeLists.txt file to the mobile-service repo
• Send a gerrit change to update the TLM CmakeLists.txt file to include building the mobile-service CMakeLists.txt file