* 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