dns: add names for common types

Add names for SRV, NAPTR, DS, RRSIG, NSEC, NSEC3 types.
dns: unify type to string logging utility

Both DNS loggers had their own CreateTypeString. This patch unifies
them.
nflog: warn if buffer-size is larger than max-size

If buffer-size is larger than max size, give a warning and adjust
buffer-size to max-size.
nflog: set socket timeout

Set socket timeout so that we can exit if there is no traffic.

It would hang after the SIGINT signal, until packets arived.