This patch makes a number of changes in the engine surrounding the
resource API. In particular:
* Cleanup of send/read event.
* Cleanup of DoSend (now Event) in the Watch method.
* Events are now more consistently pointers.
* Exiting within Watch is now done in a single place.
* Multiple incoming events will be combined into a single action.
* Events in flight during an action are played back after CheckApply.
* Addition of Close method to API
This gets things ready for rate limiting and semaphore metaparams!
This removes some boilerplate from the Watch methods which can be baked
into the engine instead.
This code should be checked for races and locks to make sure we only
start resources when it makes sense to.
This takes the Converged initialization and Startup patterns that are
common in all resources, and bakes it into the core engine. This way
resource writing is much more concise and there is less boilerplate!
