QtumJS support for Ethereum

[hayeah]

It would be an interesting exercise to reimplement QtumJS's RPCs to make it work in MetaMask.

The RPC methods related to invoking a contract's methods are:

• callContract
• sendToContract

Confirming A Send Tx

The send API looks like

  const tx = await myToken.send("mint", [toAddr, amount])

  console.log("tx:", tx)

  // Wait for 3 confirmations. The callback receives the
  // updated transaction info for each additional confirmation.
  //
  // Both arguments are optional. `await tx.confirm()` would do.
  const receipt = await tx.confirm(3, (updatedTx) => {
    console.log("new confirmation", updatedTx.txid, updatedTx.confirmations)
  })

The confirm method is implemented in TxReceiptPromise

Because the QTUM RPC calls return very different data than Ethereum's RPC, it's probably more realistic to fork qtumjs, and implement a few things as an experiment.