[feature request] Implement exception handing in RPC callbacks

[jsturdy]

Brief summary of issue

To better handle error conditions and unexpected behaviour, we should implement common exception types, and some handlers for cases where a usual course of action needs to be taken.
The RPC method should always be handling the received exceptions and setting the error key in the response message (or handling, if it is appropriate for the method)

Types of issue

• Feature request (request for change which adds functionality)

Expected Behavior

• Local methods should not set an error key in the RPCMessage response
• RPC callbacks should set the error key in the RPCMessage response in the event of an exception or error in the local method

Current Behavior

Some local methods return error codes, some set the error key, and some throw an exception.

[bdorney]

Isn't this a duplicate issue to #85?

[bdorney]

Some local methods return error codes, some set the error key, and some throw an exception.

Additionally which methods throw? None come to mind presently. I'm only aware of those that set the error key.