Proxy tendermint rpc calls

[ethanfrey]

We should add another command (proxy) that mirrors the exact tendermint rpc.

It would call a real node and do validation of all signatures before forwarding the response (now trusted) or returning an error.

It will expose binary(hex) data for broadcast_tx and abci_query. We want to verify the following calls (others just pass through). This must also work over the websocket connection.

• blockchain
• block
• tx
• validators
• abci_query

Events to validate:

• new_block
• new_block_header
• tx

[ethanfrey]

Basic rpc calls with validation implemented on commit a17db62

Still needs active testing, check websocket support.

[ethanfrey]

Seems to work with real-world clients.