Convert Liquity Solidity smart contract to USJ CW contract

[Jammyaa]

I. Task description

Convert Liquity Solidity smart contract to USJ Cosmwasm contract for our first review.

II. Task timeline

Deadline: 27/6/2022. 28/6 is ready for discuss.

III. Task goals

• [ ] Completed all works ahead of time

[Jammyaa]

List of basic completed tasks at 28/6:

• ActivePool contract: The Active Pool holds the JUNO collateral and USJ debt (but not USJ tokens) for all active troves.
• DefaultPool: The Default Pool holds the JUNO and USJ debt (but not USJ tokens) from liquidations that have been redistributed to active troves but not yet applied, i.e. not yet recorded on a recipient active trove's struct.
• CollSurplusPool: The Coll Surplus Pool holds the JUNO surplus from Troves that have been fully redeemed from as well as from Troves with an ICR > MCR that were liquidated in Recovery Mode.
• JunoSwapOracle
• USJ Token Implemetation
• usj-base generic package

Tasks in progress:

• Write tests for all completed contracts and modify contracts if logical errors are found.
• Enable both CW20 and ICS20 token as collaterals.
• BorrowerOperations contract.
• TroveManager contract.
• StabilityPool contract.