Side effect: the log dialog now has an icon
indicating whether there are errors or warnings.
A new utility widget has been introduced to
attach log messages (warnings/errors) to
dialogs. This widget is a QToolButton that
is invisible initially. It provides warning
and errors channels and can be fed messages.
If errors or warnings are fed, the tool button
becomes visible. If (directly) embedded inside
a QFrame, the frame's background will turn
red to indicate the region of interest.
The button can be pushed to read the log.
The button is called lay::AlertLogButton
and is found in layLogViewerDialog.h.
TODO: move to layBasic.