Merge branch: TTL mismatch handling

src/common/errcode.c

src/common/errcode.h

src/knot/dnssec/zone-sign.c

src/knot/server/zone-load.c

src/knot/updates/ddns.c

src/knot/updates/xfr-in.c

src/knot/zone/node.c

src/knot/zone/node.h

src/knot/zone/semantic-check.c

src/knot/zone/semantic-check.h

src/knot/zone/zone-contents.c

src/knot/zone/zone-contents.h

src/knot/zone/zone-create.c

src/knot/zone/zone-create.h

src/libknot/rrset.c

src/libknot/rrset.h

tests-extra/tests/zone/ttl-master/data/ttl-mismatch.zone

tests-extra/tests/zone/ttl-master/test.py

tests-extra/tests/zone/ttl-slave/data/ttl-mismatch.zone.1

tests-extra/tests/zone/ttl-slave/test.py