Event Handler needed for ResourcesUpdate events

[rherrell]

We have the ResourcesCreated Event handler working, which causes the core library to retrieve an entire tree associated with a new resource.
We need to implement the ResourcesUpdated Event handler, which will cause the core library to retrieve the latest copy of an existing resource from the resource creator and update the Sunfish description accordingly.

We leave it up to the creator of the resource being updated to update any other resources that are impacted; for instance, if the updated resource requires updating navigation links to other objects, the Sunfish ResourcesUpdated Event handler will NOT hunt those other objects down and update them. The ResourcesUpdated Event should include a list of ALL resources that need to be updated.