This is done for all top level windows - ports, stats, logs
At startup, the local portgroup would automatically become current with
the result that the welcome page would not be visible. Not sure why but
an explicit setFocus of ports window seems to avoid it.
* All 3 icons are combined into a single row instead of 3 separate rows
* Tooltip to clarify meaning of icons
* Qt Model-View displays icon left-aligned, so use a custom delegate to
center-align it
* Add a icon for "Transmit On"
* Edit icons for "Start/Stop Capture"
- Automatic full column selection
- Enable/Disable toolbar buttons based on selection
- Code refactoring to avoid unncessary selectedColumns computation
