Conflicts:
	src/libknot/dname.c

RRSet from wire refactoring

Refactored conversion functions for parsing RRSet from wire according to older code and moved from/to wire functions to `packet/`. Also unified a bit with the 'to wire' functions (common RDATA-traversing function).

Also takes into account issue #289.

Fixes #228.

See merge request !275

Rrset dump refactoring

See merge request !277

- DNAMEs are now always decompressed and then there's a check if
  compressed and decompressed sizes match, in case they shouldn't have
been decompressed in the first place.

- It is possible to create an RR with compressed DNAME in it, that would
  be actually bigger than 2**16 - 1. I've added a check for that.

- Tests for both mentioned cases pending.

Axfr ixfr

See merge request !276

Also refactored a bit.
TODO: Remove the use of parse_rdata() function in utilities, so
      that it may become static.