Refactor|Client: Common GuiWidget opacity

The console command line is made more transparent when it is out of
focus.
Client|Task Bar: Improving usability

Tweaked behavior of Shift-Esc vs. Esc: Shift-Esc no longer opens
the menu, just the task bar with the console focused.

Added a hint text to the command line editor widget to indicate what
to the user should do.
libgui|Font: Clearing a RichFormat