The goal of this task is to update writeValueToStream() to do the following:
(1) Truncate arrays and objects if they exceed a certain depth and/or if they exceed a certain number of elements/fields; and
(2) Truncate bsonRegex's and bsonJavascript's if they exceed a certain length.

We need to figure out what specific scheme we want to use for truncating arrays and objects. One option is to implement a scheme similar to what BSONElement::toString() does.

(For bonus points, it would be nice to also fix writeValueToStream() so that it actually prints out the contents of a jsFunction instead of just printing out "jsFunction".)