HIP-19 Revamp Hedge Strategy

This HIP is to replace the previous HIP-5 (https://hummingbot.discourse.group/t/hip-5-dg-fix-and-improve-hedge-strategy/51) which further improves the use of this strategy.

A working version has been prepared at https://github.com/leastchaos/hummingbot-1/tree/new_hedge 8

The main improvements in this hedge strategy over the existing hedge strategy are as follows

1. Cython → Python; Simplified codebase for easier modification.
2. One exchange → Multiple Exchange: Allow hedging of multiple assets at multiple exchanges at the same time
3. Hedge by amount → Hedge by amount or value: Allow hedge based on the current asset value in quote asset.
4. Remove restriction on spot/perp on both maker and taker: Able to select both spot and perpetual for both monitored market and hedge market
5. Added fixed offset: Allow maintaining of a fixed net amount of asset amount/value.
6. ONEWAY mode -> ONEWAY/Hedge mode: Allow both position modes to be used

HBOT amount requested: 400k HBOT Total