This commit moves the query routes backend logic from the main
rpc server into the sub server. It is another step towards splitting up
the main rpc server code.
In addition to this, a unit test is added to verify rpc parameter
parsing.
In this commit, we implement the full RouterServer as specified by the
newly added sub-service as defined in router.proto. This new sub-server
has its own macaroon state (but overlapping permissions which can be
combined with the current admin.macaroon), and gives users a simplified
interface for a gRPC service that is able to simply send payment. Much
of the error reporting atm, is a place holder, and a follow up commit
will put up the infrastructure for a proper set of errors.
