- RRSet function removed altogether, it was not needed.

- 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.

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

- 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

- Will leak
- Untested

The config.h is now implicitly included using -include option of the
compiler. After this change, config.h need not be placed at the first
position in all source files.

- RR insertion function now returns zone RRSet.
- Removed reduntant zone contents / node API functions
- Cleanup.

- 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)

issue #1

- Cleaned up some sem check functions - check level no longer needed,
  removed needless handler init parameters
- Added a better check for DNAME children error
- Sem. errors no longer ignored, will trigger bootstrap replan
- IXFR probably has its own checks, will inspect later
- Removed some weird assertions and philosophical questions in comments

Error message is already terminated by exclamation
mark. We cannot tell anything about data.

Fix unchecked output value of snprintf() detected by Coverity.

CID #1140397

CID #1134442