Enabled the use of Debugger-specific watch/locals models.
- Modified WatchModel to handle storage of an hierarchy of WatchItems. - Factored out code for asynchronous population to AsyncWatchModel and added a mixin for convenient handling - Added base class for synchronous models. - Implement simple, synchronous models for CDB, greatly simplifying code and finally getting manual expansion right. Signed-off-by: hjk <email@example.com>