- knot_rrset_copy now returns pointer

- knot_rrset_create_rr removed, only way to insert RR into rrset now is
  when you already have RDATA, so that we never create RRSet that is not
sorted.
- rr.h doxygenated, functions moved around a bit.

 - merging can now be done directly using knot_rrs_t

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

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

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

- use rrset initialization macro instead, or create rrset explicitely

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

- previously static function 'put_rr' in internet.c has been made public, it handles additions of RRSIGs as well now, by adding the to a list that is traversed after each section has been solved.

- Removed rrset->rdata_indices, RDATA lengths are now stored inline together with RR's TTL
- Added function to get RR's TTL - TTL of the whole RRSet can still be obtained, but it will default to the first RR's TTL or 0
- Renamed few RRSet functions, removed a few too - the file still needs a cleanup and function reordering
- Special handling for RRSIGs during AXFR-out no longer needed (yay)

- RRSIGs from node are added to rrinfo section.
- When putting RRSIGs for each section, proper RRSIGs for each RRSet are syntesized and later freed.

- Added new public alloc helper functions to mempattern.h.
- RRSet owners are not allocated using memctx, because they might be dropped later and because DNAME has no memctx API.
- Only packet had its own memctx at the time of writing. Later, most RRSet operations should use custom allocators, for now, no allocator is used.

Should be obsolete now and should work without them.

refs #168

Coccinelle patch performing most changes included.

Not optimal, uses existing interface for RRSet merging.

refs #4

Allows to create a new emtpy RRSet given another RRSet as a template.

- uses knot_dnssec_sign_verify() instead of string comparison
  and therefore OpenSSL EVP_VerifyFinal()
- previous approach could not work e.g. for DSA based ciphers

refs #4

- Zones are now automatically (re)signed when server starts/reloads
- Signature validity check now calculates the signature as well - this is used to detect changes to RRs themselves
- 'knotc signzone' issues a force signing of zone - all RRSIGs are dropped and recreated
- Some leaks and bugs still present, but the code is commitable now

Refs #4

- needed for zone diff and DNSSEC
- knot_rrset_deep_free_no_sig() already exists

refs #2413

Change-Id: I3d97bc4ea2f0986900c503bd10bc5f5ceb2585a6

Also simplified, cleaned and fixed.

refs #109