Added "sh" command. This is similar to "bash" but splits stdout into a list.
Added string_list to help, as the reader updates the history.
Added "load" and "use". "load" is more general and will read a file as
lisp source. "use" is the equivalent to (load (str file ".gk")) but has
been added as a special form to allow for (use "core").
Added a count function. Could be more efficient, but it's nice to see
it build from existing components (reduce and inc).