- knot_rrset_copy now returns pointer

Conflicts:
	src/knot/zone/zone-contents.c
	src/libknot/packet/pkt.c

No Default Nsec3 Tree

Two parts:

* Growable hash node size in trie
* NSEC3 tree created only if needed (NULL is treated as an empty tree)
  * I'm not sure if I did the zone-diff stuff right? :suspect:

- 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

http://www.ucw.cz/gitweb/?p=libucw.git;a=blob;f=ucw/bigalloc.c;hb=HEAD

Leaf hhash node size is growable (1-4 pages).
The rule is simple, when a hashtable is split the left and right
children size is clamped left and right weight to the nearest
hhash size. The sizes are chosen arbitrarily so the table size
is always a multiple of page size.

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

Don't merge RRs in the incoming packets

- 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

- misleading statement
- module name in heading
- s/forward\./example./g