Add guards to generated Observers - exceptions, threads with timeouts

[GoogleCodeExporter]

In generated Observer code, set up try/catch blocks inside the loop so 
exceptions won't stop notification to other listeners.

Also -- some listeners may perform long-running ops; add option to start a 
thread for each listener and timeout if needed.

Original issue reported on code.google.com by scott%ja...@gtempaccount.com on 3 Nov 2008 at 5:05