Merge branch 'nsec_sign_changesets' into 'master'

src/knot/dnssec/nsec-chain.c

src/knot/dnssec/nsec-chain.h

src/knot/dnssec/nsec3-chain.c

src/knot/dnssec/nsec3-chain.h

src/knot/dnssec/zone-events.c

src/knot/dnssec/zone-nsec.c

src/knot/dnssec/zone-nsec.h

src/knot/events/handlers/load.c

src/knot/updates/apply.c

src/knot/zone/contents.c

src/knot/zone/node.c

src/knot/zone/node.h

tests-extra/tests/dnssec/nsec_update/test.py

tests-extra/tools/dnstest/server.py

tests-extra/tools/dnstest/test.py

tests-extra/tools/dnstest/zonefile.py