Add `wallet_` methods to improve dapp to wallet interaction

[pedrouid]

Just created a separate thread for EIP-2015 [wallet_updateChain].

EIP-2015: Wallet Update Chain JSON-RPC Method (`wallet_updateChain`)

The EIP is looking good so far and I’m happy with the specification to be implemented. I would only suggest that we keep JSON-RPC requests consistent and only use hexadecimal encoded values on the parameters. Just as eth_chainId returns the chainId value hex encoded, we should also pass this parameter and networkId on wallet_updateChain value hex encoded. However as @danfinlay pointed out here, the EIP-747 uses decimal values but I since this EIP is also on Draft, I personally would like to s…