Added functions to betterbatch and debugging on the horizon

I was expecting function to be not so hard (just another way of
running a few steps) but it took a little bit of time all the same.

I got it implemented (though no tests for it yet) and it seems OK, I
will know better how it works when I get around to using it (hopefully
in the next week). Weekends for the tool and weekdays for using the
tool in production :)

With this addition I think the language definition is more or less
complete I think. I can imagine tweaking it a bit, fixing bugs etc,
but I don't expect to implement many other language constructs.

One of the next things that I am planning to implement is a simple
debugger (step through statements, print variable value, maybe change
variable values, etc). I was expecting this to be a fairly major
undertaking but again Python and it's community come to the rescue.
Right on cue

a) Catherine Devlin mentioned cmd2 on her blog,
http://catherinedevlin.blogspot.com/2008/01/introducing-cmd2.html
which made me look at cmd in the Python standard library
b) I found the Python documentation a bit dry (or else I had very
little patience) so googled for some examples - and Doug Hellmann's
excellent PyMOTW (http://blog.doughellmann.com/2008/05/pymotw-cmd.html
if you don't know it - bookmark it!) popped up with some good examples
and great documentation.

I found that I was able to throw together a simple debugger (next,
print_var, print_vars, etc)

So this means that a debugger is really easy to write - and is a much smaller task than I was hoping. Maybe next weekend I get the debugger implementation finished.