GETPROPLIST Return list of available properties

     PL=GETPROPLIST(DATA)
     PL=GETPROPLIST(DATA,'feat')
     PL=GETPROPLIST(DATA,'data')

 INPUT
   DATA     Data set

 OUTPUT
   PL       Cell array with property names

 DESCRIPTION
 GETPROPLIST returns the list of properties in DATA.  By default, sample
 properties are returned. With additional parameters, GETPROPLIST may
 return also feature or data properties

 SEE ALSO
 GETPROP, SETPROP