Description: Add a symbol on shortcut to help distinguish call states for color blind users.
A symbol will also appear on DDI shortcut whether there are linked to a "Subscribed" or "Monitored" line, if there is no other call state symbol displayed.
This symbol will take precedence of the specific contact shortcut's symbol "C" if displayed.
Constraint: none|ringing|all
none: No symbol is added to shortcut for displaying call state
ringing: Add a symbol "R" to shortcut in "ringing" state
all: Add a symbol to shortcut to distinguish states ringing, incoming, established, outgoing, held, subscribed and monitored (the two last one only apply on DDI slot shortcut)
