Conflicts:
	src/libknot/zone/zone-contents.c

Conflicts:
	src/libknot/zone/zone-contents.c
	src/libknot/zone/zone-contents.h

Conflicts:
	src/knot/server/zones.c

Conflicts:
	src/knot/server/zones.c
	src/libknot/dnssec/zone-events.c
	src/libknot/dnssec/zone-keys.c

Closes #184

Conflicts:
	src/knot/main.c

Increase the expire time for zones with very short expiry. Without
this a zone may expire if there is a timeout, and once it has expired
it won't be served until it is refreshed. Sometimes, customers load
zones with SOA values that we have little control over.

Signed-off-by: Jan Kadlec <jan.kadlec@nic.cz>