Removed Firewaller API V0
Merge pull request #849 from dimitern/drop-firewaller-api-v0

Removed Firewaller API V0

Follow-up to #846, this removes the API version 0 of
the firewaller API facade, as it's no longer used.

NOTE: Already approved as http://reviews.vapour.ws/r/110/.
This PR just re-targets the branch against juju:master