Merge branch 'unreachables' into 'master'

Knot.files

Knot.includes

doc/man/knot.conf.5in

doc/reference.rst

src/contrib/sockaddr.c

src/knot/Makefile.inc

src/knot/common/unreachable.c

src/knot/common/unreachable.h

src/knot/conf/schema.c

src/knot/conf/schema.h

src/knot/query/requestor.c

src/knot/server/server.c

src/libknot/errcode.h

src/libknot/error.c

tests-extra/tools/dnstest/server.py

tests/.gitignore

tests/Makefile.am

tests/knot/test_requestor.c

tests/knot/test_unreachable.c