Coordinate `PHOTWAPOracle` && `PriceController` wrt TWAP `period`

[steve0xp]

It is required that the PriceController and PHOTWAPOracle have synced period variables. The PriceController calls stabilize() in a time frame respective of the PHOTWAPOracle period. Care has to be taken to ensure that if/when the PHOTWAPOracle period var is set, that the PriceController also syncs up with this new change.