Service decoding error handling

[kurtkilpela]

If a service is decoded and the expected properties of a service do not match (e.g. number of instance variables), we close the RsrConnection. This has made debugging harder for myself and for Eric.

If an error happens decoding a message/service, we should do the following:

1. Don't apply any updates that would have been the result of the associated message.
2. Don't send the associated message.
3. Return an error message to the sender with a useful message.

[martinmcclure]

That seems like it would open a debugger on the side sending the message. This is useful. It might also be useful to open a debugger on the side receiving the message, since messages can flow either way. When debugging the framework, you might have one side GemStone, the other side Dolphin. Dolphin can obviously open a debugger. If the GemStone side was using GBS or Topaz, a debugger could also be opened there without relying on RSR itself.

[kurtkilpela]

Yeah. It makes sense to have a hook where we can either open a debugger or return an error.