Merge branch 'events-cleanup' into 'master'

Knot.files

src/Makefile.am

src/knot/nameserver/update.c

src/knot/zone/events/events.c

src/knot/zone/events/events.h

src/knot/zone/events/handlers.c

src/knot/zone/events/handlers.h

src/knot/zone/events/replan.c

src/knot/zone/events/replan.h

src/knot/zone/zone.h

tests/zone_events.c