UI|Client: Added a stub from the alerts dialog
Default Style: Revised the VR icon
UI|Client: Configurable styled log sink formatter
Cleanup
UI|Client: Improvements for label and menu widgets

One can now specify a fixed maximum width for a label’s text, and
menus can show plain labels instead of just buttons and separators.
UI|Client: Alert notification for logged warnings and errors

This is the basic implementation of the alert mechanism. All warnings
and errors entered in the log show up as alerts in the main window’s
alert notification dialog.