- merging can now be done directly using knot_rrs_t

 - tests are passing, however some work is still pending, namely storage
   of additionals for freeing.
 - removed some obsolete node API functions

- if adding apex NS, adjust counter

- Do not merge incoming RRs
- Duplicated add/remove checks improved in ddns
- Remove stuff directly from RRSet, do not return

- removing and adding already existing record
- leak solved, but need to move old a new data lists from
  zone_contents_t

- only basic functionality with leaks

- sem checks missing, more extensive tests missing

- most checks can be done without allocating anything

- Lost my temper with the direct changes, rewritten DDNS to only
  changeset creation, application will be the same as usual.
- Will not work now

- not perfect, but without this there'd be no way to tell whether to
  free the owner or not.

updates.

- DDNS and changeset application will not work now, but it wouldn't work
  before either

- some cleanup and fixes as well, namely simplified RR creation during
  zone load (no malloc)

- RRSet copies removed, packet now stores rrsets directly (structure is
  copied, but copy is shallow)

- use rrset initialization macro instead, or create rrset explicitely

- kept RRSet copies somewhere (node has to create them now)
- replaced knot_rrset_t with knot_rrs_t elsewhere
- semantic checks simplified

- simplified all the functions while I was at it

- Will leak
- Untested

- new types: knot_rr_t and knot_rrs_t
- these can be used in the node structure instead of knot_rrset_t

New Dnssec Tests