GitLab

Because:
- We keep seeing random timeout errors in production.
- It's better to retry operations that time out a few times before
  giving up completely - this runs in the background sending cron mail,
  so we should try to take care of our own problemns ;-)

Because:
- simeple_rest_client raises generic "ClientConnectionErrors" on read
  timeouts. The real reason is only discoverable by checking the
  exception's __cause__.

Because:
- It's not clear whether the implicit timeout in the underlying library
  is "infinite" or some arbitrary value, but we keep getting timeouts
  in production.

Because:
- The newest version of simple_rest_client seems to have requirements
  that cannot be satisified.
- We don't know that this code is compatible with simple_rest_client
  1.0.0

Because:

- NAV 5.0 drops SNMP attributes as part of the Netbox model, introducing
  the concept of management profiles. Kindnavsync needs to be able to
  work with both pre-5.0 and post 5.0-versions of NAV for now.

Support for older NAV versions can be dropped later.

Also update to a trove license classifier that matches the actual license.

Viste seg vanskelig å debugge disse feilene mot en testserver :)

also ditch IPy in favor of ipaddress, which is built-in in Python 3

having timestamps in the log output will cause kindnavsyncdiff to trigger on
every run, even though the output is in fact the same.