Explicit Opt Out of Auto-Transactions for Specific Handlers

[jeremydmiller]

Easy money, just have a way to opt out of being transactional.

[jeremydmiller]

Tasks

1. Add a new [NonTransactional] attribute parallel to TransactionalAttribute
2. Add a new value of None to TransactionMiddlewareMode
3. Change the IChain.IsTransactional boolean to using the TransactionalMiddlewareMode. Rename the prop to Mode
4. New attribute should set the IChain.Mode to None
5. No transactional middleware should be applied to any IChain that is decorated with [NonTransactional].
6. All transactional middleware should respect the presence of the NonTransactionalAttribute and not apply any middleware