* Added basic Escrow
* PullPayment now uses an Escrow, removing all trust from the contract
* Abstracted the Escrow tests to a behaviour
* Added ConditionalEscrow
* Added RefundableEscrow.
* RefundableCrowdsale now uses a RefundEscrow, removed RefundVault.
* Renaming after code review.
* Added log test helper.
* Now allowing empty deposits and withdrawals.
* Style fixes.
* Minor review comments.
* Add Deposited and Withdrawn events, removed Refunded
* The base Escrow is now Ownable, users of it (owners) must provide methods to access it.
