Propose Recoil for Global State

[MorganIsBatman]

This is a proposal for adding Recoil (https://recoiljs.org) for global state, with a couple of hooks set up to demonstrate its use, so we have a basis for conversation.

Recoil is created by Facebook (creators of react) to be the goto state-management lib for react. It does away with a lot of redux' boilerplate for an API that at its most basic resembles useState (but with selectors and more advanced usage available).

In this PR:

• useMetamask: A hook providing functionality so a user can connect their metamask wallet, and access the account, provider and signer anywhere in the app using either the hook, or useRecoilValue
• useContract: A hook to abstract the common code when connecting to contracts

[MorganIsBatman]

useRecoilValue is a hook if you only need to READ state, whereas useRecoilState is a simile to useState, giving you [state, setState] equiv