Add couchbasedeps repos for grpc

The mobile-service requires grpc, which will need the following repos mirrored in couchbase deps:

<remote name="golang_grpc" fetch="git://github.com/grpc/" />
<remote name="google" fetch="git://github.com/google/" />

<project name="grpc-go" remote="golang_grpc" path="godeps/src/google.golang.org/grpc"/>
<project name="go-genproto" remote="google" path="godeps/src/google.golang.org/genproto"/>

I was able to build the mobile-service code using this manifest:

https://github.com/tleyden/manifest/blob/5c6e8a25728b5ab910552c61277316524d2ae06e/couchbase-server/mad-hatter.xml

(I'm planning to rework that manifest to point to the couchbasedeps repos once they are created)