- Introduce constants for task categories, add "RunTime".
- Log exceptions under "RunTime".
- Clear pane on debugger start.
- Add 'first chance'

Task-number: QTCREATORBUG-8141
Change-Id: Icf68def06c42a0f3bb86dcc2ae74750b5397ca52
Reviewed-by: hjk <qthjk@ovi.com>