partitionString

Splits a string list into two lists based on a predicate. The first list contains elements matching the predicate, the second contains the rest.

Example:

    var pair = Lists.partitionString (list, (s) => {
        return s.has_prefix ("a");
    });
    // pair.first = items starting with "a"
    // pair.second = all others

Parameters:

list	the source list.
fn	the predicate.

Returns:

a Pair of (matching, non-matching) lists.