update Dockerfile with cryptopp and jsonrpc dependencies, fixes #423

@subtly note that the actual patch is commented out. With Allow-Origin you could connect to the JSONRPC API from non-localhost; ideal when using the eth.js proxy for debugging / development. Note that pyethereum's apiserver also sets this header:
https://github.com/ethereum/pyethereum/blob/master/pyethereum/apiserver.py#L57-60