Merge branch 'kzonecheck' into 'master'

doc/man/knot.conf.5in

doc/man/kzonecheck.1in

doc/man_kzonecheck.rst

doc/reference.rst

src/knot/dnssec/rrset-sign.c

src/knot/dnssec/rrset-sign.h

src/knot/dnssec/zone-keys.c

src/knot/dnssec/zone-keys.h

src/knot/events/handlers/refresh.c

src/knot/zone/semantic-check.c

src/knot/zone/semantic-check.h

src/knot/zone/zone-load.c

src/knot/zone/zonefile.c

src/knot/zone/zonefile.h

src/utils/kzonecheck/main.c

src/utils/kzonecheck/zone_check.c

src/utils/kzonecheck/zone_check.h

tests/semantic_check_data/cdnskey.cds

tests/semantic_check_data/cdnskey.invalid

tests/semantic_check_data/cdnskey.invalid.param