Request from Jae:

Add rpc call to query a merkle proof given a optional block height (defaults to last commited). If this height is available, return an serialized proof, if it is not available, return an error.

Tendermint rpc must proxy to the tmsp app, which needs to support it.

Demo this functionality in a branch of merkleeyes.

Then some client test.

All work will be done in branches tmsp_proof