Mist web3 loading proposal

mistweb3.js

/*
Basically "web3" comes from Mist,
but "Web3" CAN come from  the dapp.

A Dapp has 3 ways to use web3.
2. and 3. would work when in Mist and outside.
*/

// 1. simply use, web3 comes already defined
web3

// 2. optional use web3 from mist, OR load if outside of mist
if(typeof web3 === 'undefined')
  web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));

// 3. always use web3 provided by the dapp ("Web3" won't be supplied by Mist), but the provider from mist
if(typeof web3 !== 'undefined')
  web3 = new Web3(web3.currentProvider);
else
  web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
  
// Add RPC version?