In some cases we only have a string collection instead of a string list
that we want to serialize out. We have a convenience method for writing
a list of strings, but no such method for writing a collection of
strings. Yet, a list of strings is a collection of strings, so we can
simply liberalize StreamOutput#writeStringList to be more generous in
the collections that it accepts and write out collections of strings
too. On the other side, we do not have a convenience method for reading
a list of strings. This commit addresses both of these issues.
169cb38778