Account-Abstraction release 0.5.0

This version contains several important changes to the account and entrypoint. It is also audited by OpenZeppelin (see the audits in the audits folder)

Below are the Major Changes:

Changes to IAccount

• IAccount.validateUserOp changes:
  • removed the "aggregator" parameter.
  • No longer revert on signature error, but report it as a return value.
  • The return value from it is time-range, signature success/failure and (possibly) aggregator.

Changes to Paymaster

• IPaymaster.validateUserOp changes:
  • Like the Account, the return value defines a time-range and signature success/failure
  • Note that in case of signature failure (as in a case of VerifyingPaymaster, it is flagged through return value, and not revert.

Changes to IEntryPoint

• added simulateHandleOp, to simulate a full UserOperation execution (not only validation)
• (and all the API changes required by the above interface changes)