Enhancement suggestion: @format and @formatn

#1
Currently if the 2nd parameter is an undefined variable both the @FORMAT and
the @FORMATN functions display an error message. I suggest adding an
optional 3rd parameter to specify default value. This would remove the need
for considerable error checking. Alternate solutions: 1/ new functions with
the desired behavior; 2/ .INI directives or "TREEEXCLUDE" type variables to
specify default value; 3/ additional control element in 1st parameter to
specify default behavior.
--
Steve