"public" field means that this zone can be used by every user (not just the owner) to create hosts there
"available" field means that the nameserver is operating and reachable
remove unneeded stuff from settings
(we still need some in conftest.py for the tests, though)
init DB for tests via conftest.py
more update algorithm choices
give origin zone (if we already know it) to dnstools functions
new views: DomainOverview, DeleteDomain
unify deletion templates using delete_object.html
add django-extensions