all math implemented : bugs/todo in description

1. Each math dir needs to have a doc
2. Multiply crashes when you call it with non-integer values.
3. Factor is normally called with 1 arg. Yet, our mathfs insists that
anything with 1 argument is a directory. We could hack in a solution and
add /junkArg2 to the input (before feeding it thru parser) if we see
/factor in the input string.