#306 Debugger should trap exceptions and allow program inspection

[Nicolas Chapados]

The pydev debugger would be considerably more useful if there was a means of trapping exceptions as they are raised and allow the user to inspect program state (local variables, stack, etc.) at the point of raising.

Note that this feature is available in the cross-platform winpdb Python debugger, so should be possible to implement (without too much trouble?).

(Even more useful would be a 'fix-and-continue' system for Python, just like Visual Studio, but this is reportedly difficult to implement.)