STYLE: relegate special purpose readList<T> function to points of use

- the readList<T>(Istream&) function was introduced to handle command
  -options with either a single or a list value, but was also used for
  the #remove dictionary directive. However, the parsing was fragile
  if the list did not start with a '('.
  Now handle command-line arg/option list directly (via ITstream)
  and #remove with special-purpose reading of a string or word list.

  This removes ambiguity and reduces potential future problems.

STYLE: use ITstream instead of IStringStream for command-line lookups

- parses directly to a tokenList without a string copy.