SHA3 stuck on flawed "binary" encoding

[gavofyork]

parity.api.util.sha3 interprets its argument as 'binary' information. This is problematic since there are certain binary blobs that JS cannot encode as a string, which get opaquely coerced to some other string.

web.sha3 addresses this by interpreting 0x prefixed strings as hex-encoded data - other inputs are assumed to be binary-block strings.

It should probably be consistent with web3.sha3. Failing that, it should remain consistent with the JSONRPC's conventions and only accept hex-encoded data.

[tomusdrw]

Seems that web3.sha3 has an additional option to indicate that data is hex-encoded bytes: https://github.com/ethereum/web3.js/blob/develop/lib/utils/sha3.js#L26

Looks like we already do something similar:
https://github.com/ethcore/parity/blob/master/js/src/api/util/sha3.js