refs #109

refs #109

Conflicts:
	src/libknot/rrset.c
	src/libknot/rrset.h
	src/libknot/updates/ddns.c
	src/libknot/updates/xfr-in.c

Would need changes. Better to do after all RRSet refactoring is
done.

refs #109

refs #109

refs #109

Also simplified, cleaned and fixed.

refs #109

refs #109

- Removed some now-unused functions (next_dname..., dnames_apply)
- Added basic comments to some function headers.

Not finished, does not compile.

refs #109

Not very usable yet (some RRSet functions have been changed, some
haven't been), but the compiles and server loads zone successfully.

refs #109

Only rrset.h conflicts resolved!

Conflicts:
	src/libknot/rrset.h
	src/libknot/updates/xfr-in.c
	src/libknot/zone/zone-contents.c

This is because most of the packet is now not double-buffered,
so query wire is required to remain intact during processing.

All dnames are now duplicated instead of refcounted,
this is excessive for some cases but should be refactored later on.
For example node and all its RRSets have the same owner but each its
own copy.

Also correct size calculation of dname parse of compressed data.

The packet size was previously zero and question size included
header size.

* xfrin_add_new_node and ddns_add_new_node were duplicates
  - knot_node_set_zone() was called in the _add functions anyway
* merged checks for NSEC3-related RR to knot_rrset_is_nsec3rel()
  - the empty RR check was pointless, as even if empty, the node
    shouldn't be searched in normal tree