Audit the price path

Src/SwarmFeed.sol, src/PriceFeed.sol, src/NhiFeed.sol, src/SpotFeed.sol, src/SwarmRelay.sol, src/OracleAsker.sol, src/UsdPriceFeed.sol, src/SharePriceFeed.sol, src/SwarmWorkOracle.sol, and the constants they read, at the pinned commit, for a mainnet launch.

Implemented and tested contracts

ABI documentation and an independently reviewed launch.json.