The delegate was still rendering display text. But we didn't realize
because the only place where this delegate was used was returning a
QVariant() for DisplayText role earlier. Once we started returning a
valid QString (for copy-paste purposes), this bug showed up.
This didn't work because we further delegate the actual painting to
the base QStyledItemDelegate which re-initializes option.features
from the item index values, so removing HasDisplay does not work.
The fix is to override the displayText() to return a null string.
* 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"
