Implement batching, protocol asset tracking, and ratio withdrawals

[jakekidd]

• Have changed 'execute' to 'open'
• Now have batch struct input for open and close: stores protocol and amount
• Now track protocol assets stored locally, child contracts are expected to pass their asset (e.g. LP tokens, aTokens, etc) back to QWManager. Note that this will be different for staking, however, as no tokens are returned...
• We do ratio withdrawals. Since user ownership % of the investment pool for a given protocol will be the thing we track off-chain, we now withdraw not in amount of tokens but in % of the total pool.
• Every protocol now has a designated "investment token" which is expected to be given to purchase LP tokens for example, and expected to be the token received when we withdraw, making it also the liquidation token

In line with spec: https://docs.google.com/document/d/1ph0YBSK93mUuKtnnJqtEYL87gR_my0SHbYOpzvA0wdI/edit