A number of changes getting ready for a new ipcluster....
A number of changes getting ready for a new ipcluster.
* Added argparse.py to IPython/external
* New reuse_furls options to ipcontroller. By default the controller will now delete all
old furl files unless the -r flag i given. This is needed so engines starting up don't
pick up the old furl files.
* Minor logic changes in ipengine and engineconnector related to detecting errors relating
to furl files.
