CIRCLE / django-sshkey

This brings it back on parity with django-sshkey-lookup

Putty and some commercial SSH implementations use the RFC4716 format, or SSH2
compatible public key format, for their public keys instead of the OpenSSH
public key format.

This change allows RFC4716 public keys to be entered into the key field.  The
key will be translated to OpenSSH format before being stored.

Move sshkey_fingerprint from models.py to util.py. util.py cannot import from
models.py without Django complaining about DJANGO_SETTINGS_MODULE; this is
required by the scripts. The reverse can happen fine though.

- lookup.py was deprecated in favor of setuptools entry_points; the code for
  lookup.py was moved to django_sshkey.util.lookup_main
- lookup.sh was renamed to django-sshkey-lookup since setuptools retains the
  names of scripts once installed. A symlink has been left in place.