[MetaMask Connect] Decouple UI from the “active account”

We will be using the connected account which is different for each connected dapp

- Start with dapp requests:
- Send transaction
- Sign
- Others
- Example
- Dapp uniswap.exchange requests
- eth_sendTransaction
- Params: [txParams, FROM account]
- Compare FROM account === connected account (we can put it as a constant)
- If they are the same then requests popup appears
- When user confirms the transaction, we need to make sure the transaction is submitted with the connected account

Right now, when we submit, it gets the active account (we need to modify this)
ETA 2-3 weeks