TODO

Lending logic:
  g when a token has < 18 decimal places, and a user withdraws their full EToken balance, 0 out the remaining dust so user gets a storage refund

Exec
  ? in batch dispatch, returning values probably doesn't make sense. use logs instead
  * tests
    * test that internal modules cannot be called through dispatcher or batch dispatch
    * failure cases in batch

RiskManager:
  ? how to determine which uniswap pool (fee-level) to use when market activated? check liquidity?

Liquidation
  * self-collateralisation
  ? expose bonus breakdown via LiqOpp
  ? if health score would decrease post liquidation, allow entire position to be liquidated

Tokens
  ? implement permit() on E/DTokens

Invariants to add to InvariantChecker.sol contract
  * If a user has a non-zero borrow owed:
    * they must be entered into market
    * must have a non-zero interest accumulator
  * If totalBorrows > 0, must have a non-zero interest accumulator

Pre-release checklist
  * Make sure nothing is done in module constructors except set immutable variables, and modules have no storage variables
  * All methods that take 2 addresses (liquidations/transfers/approvals) should verify they aren't == or sub-accounts
  * Verify every external/public, non-view/pure function in a module is marked nonReentrant
    * Some functions don't need reentrancy guard, ie: approve(), tag them reentrantOK
  * No accidental external methods inherited (nothing external/public in the Base classes, except moduleId)
  * Storage layout consistent between releases
  * Make sure "msg.sender" not present in contracts/modules/
  * Any path to increase/decrease/transfer an account's balance/borrow should do an updateAverageLiquidity() first