* 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"
* Redesign the toolbar buttons to be similar to port stats
* Show protocols with variable fields in bold
* Variable field list will always have a 'current', if not empty
* Adding a new variable field makes it 'current' for immediate edit
* Each protocol remembers its 'current' variable field
Also renamed UserRole to a more widget specific enum
