feat: Morpho leverage extension (#185)

* First version of MorphoLeverageStrategyExtension

* Adjust calculation of liquidation thresholds etc

* Set up tests for Morpho Leverage Extension

* add engage tests

* Fix some engage tests

* rebalance tests

* Simulate price change in rebalance

* All rebalance tests passing

* Add iterateRebalance tests

* Add ripcord tests

* Add disengage tests

* fix failing tests

* tests for setter methods

* test shouldRebalance

* test shouldRebalanceWithBounds

* test #getChunkRebalanceNotional

* fix open TODOs

* Minor code cleanup in smart contract

* Adjust docstring on _calculateMaxBorrowCollateral method

* Adjust more comments

* Adjust collateralValue to be correctly denominated in borrow asset units

* Remove unnecessary sync call from test

* Cosmetic changes to smart contract code

contracts/interfaces/IMorphoLeverageModule.sol

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: Apache License, Version 2.0
+pragma solidity 0.6.10;
+pragma experimental "ABIEncoderV2";
+
+import { ISetToken } from "./ISetToken.sol";
+import { IMorpho } from "./IMorpho.sol";
+
+interface IMorphoLeverageModule {
+    function sync(
+        ISetToken _setToken
+    ) external;
+
+    function lever(
+        ISetToken _setToken,
+        uint256 _borrowQuantityUnits,
+        uint256 _minReceiveQuantityUnits,
+        string memory _tradeAdapterName,
+        bytes memory _tradeData
+    ) external;
+
+    function delever(
+        ISetToken _setToken,
+        uint256 _redeemQuantityUnits,
+        uint256 _minRepayQuantityUnits,
+        string memory _tradeAdapterName,
+        bytes memory _tradeData
+    ) external;
+
+    function marketParams(ISetToken _setToken) external view returns (IMorpho.MarketParams memory);
+
+    function getCollateralAndBorrowBalances(
+        ISetToken _setToken
+    )
+        external
+        view 
+        returns(uint256 collateralBalance, uint256 borrowBalance, uint256 borrowSharesU256);
+
+}

contracts/interfaces/IMorphoOracle.sol

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+pragma solidity 0.6.10;
+
+/// @title IOracle
+/// @author Morpho Labs
+/// @notice Interface that oracles used by Morpho must implement.
+/// @dev It is the user's responsibility to select markets with safe oracles.
+interface IMorphoOracle {
+    /// @notice Returns the price of 1 asset of collateral token quoted in 1 asset of loan token, scaled by 1e36.
+    /// @dev It corresponds to the price of 10**(collateral token decimals) assets of collateral token quoted in
+    /// 10**(loan token decimals) assets of loan token with `36 + loan token decimals - collateral token decimals`
+    /// decimals of precision.
+    function price() external view returns (uint256);
+}

contracts/interfaces/external/IChainlinkEACAggregatorProxy.sol

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity 0.6.10;
+
+interface AggregatorInterface {
+  function latestAnswer() external view returns (int256);
+  function latestTimestamp() external view returns (uint256);
+  function latestRound() external view returns (uint256);
+  function getAnswer(uint256 roundId) external view returns (int256);
+  function getTimestamp(uint256 roundId) external view returns (uint256);
+}
+
+interface AggregatorV3Interface {
+
+  function decimals() external view returns (uint8);
+  function description() external view returns (string memory);
+  function version() external view returns (uint256);
+
+  // getRoundData and latestRoundData should both raise "No data present"
+  // if they do not have data to report, instead of returning unset values
+  // which could be misinterpreted as actual reported values.
+  function getRoundData(uint80 _roundId)
+    external
+    view
+    returns (
+      uint80 roundId,
+      int256 answer,
+      uint256 startedAt,
+      uint256 updatedAt,
+      uint80 answeredInRound
+    );
+  function latestRoundData()
+    external
+    view
+    returns (
+      uint80 roundId,
+      int256 answer,
+      uint256 startedAt,
+      uint256 updatedAt,
+      uint80 answeredInRound
+    );
+
+}
+
+interface AggregatorV2V3Interface is AggregatorInterface, AggregatorV3Interface
+{
+}
+
+interface IChainlinkEACAggregatorProxy {
+    function acceptOwnership() external;
+    function accessController() external view returns (address);
+    function aggregator() external view returns (address);
+    function confirmAggregator(address _aggregator) external;
+    function decimals() external view returns (uint8);
+    function description() external view returns (string memory);
+    function getAnswer(uint256 _roundId) external view returns (int256);
+    function getRoundData(uint80 _roundId)
+        external
+        view
+        returns (uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound);
+    function getTimestamp(uint256 _roundId) external view returns (uint256);
+    function latestAnswer() external view returns (int256);
+    function latestRound() external view returns (uint256);
+    function latestRoundData()
+        external
+        view
+        returns (uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound);
+    function latestTimestamp() external view returns (uint256);
+    function owner() external view returns (address payable);
+    function phaseAggregators(uint16) external view returns (address);
+    function phaseId() external view returns (uint16);
+    function proposeAggregator(address _aggregator) external;
+    function proposedAggregator() external view returns (address);
+    function proposedGetRoundData(uint80 _roundId)
+        external
+        view
+        returns (uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound);
+    function proposedLatestRoundData()
+        external
+        view
+        returns (uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound);
+    function setController(address _accessController) external;
+    function transferOwnership(address _to) external;
+    function version() external view returns (uint256);
+}