knotc: split into main, remote and commands

Knot.files

src/Makefile.am

src/utils/knotc/commands.c

src/utils/knotc/commands.h

src/utils/knotc/main.c

src/utils/knotc/remote.c

src/utils/knotc/remote.h

tests-extra/tests/zone/retransfer/data/example.com.zone

tests-extra/tests/zone/retransfer/data/example.com.zone.1

tests-extra/tests/zone/retransfer/test.py

tests-extra/tools/dnstest/server.py