Tidy and conformalise the toHex API.
Tidy and conformalise the toHex API.

douglas-larocca/solidity,ruchevits/solidity,LianaHus/solidity,gluk256/solidity,debris/solidity,shahankhatch/solidity,vaporry/solidity,arkpar/solidity,ruchevits/solidity,ruchevits/solidity,chriseth/solidity,chriseth/solidity-doc-test,ethers/solidity,ruchevits/solidity