Create recommended gRPC query routes/proto files

[colin-axner]

To improve interoperability and ease of integration of IBC implementations into relayers, ICS should construct a recommended set of routes and their corresponding Request and Response definitions. If IBC implementations support gRPC, they should implement the set of recommended gRPC routes/definitions to enable relayers to costlessly integrate that implementation (query wise)

Each request should contain a Height key indicating the query height the request should be performed at. The height should take into account the delayed execution models of the underlying consensus engine (if necessary). For example, ibc-go should apply the -1 and +1 to the query and proof height so that the returned proofs work for the specified height (and relayers would not need to worry about which implementations use which execution models). A height of 0 should indicate using the latest height.

All responses should contain the query value, a proof, and proof height

[cwgoes]

I agree, this would be quite nice to standardise.

[colin-axner]

Anyone have preferences for the Height field name and type?