libknot: rewrite dname to string function

New implementation can handle unprintable and special characters according to
the RFC 1035.

refs #2369 @3h
knotd: enable zone text dump

+ small code improvements

refs #2138
Possible fix to compression problems. Needs review by LS.

- Assert on line 419 in response.c was failing - added an extra check,
  so that DNAMEs with offets less than header size will not be inserted
to compression table. Seems to have fixed the issue, but I'm not sure if
I haven't broken something else. Please review.
- Reeanbled packet compression.
Fix SOA text dump

refs #2138
Remove useless code

Coverity scan #989558 (Logically dead code)
Hopefully final compression fix. Code cleanup.

- wire_pos in compression info structure was not initialized properly
  (was set to 0 instead of response->size) resulting in bogus
compression (it worked for simple records, but failed for larger ones,
if containing more than one name)
- fixed compilation warnings in debug messages.
Better clean up of useless code

Coverity scan #989558 (Logically dead code)
Fix compile warnings
utils: add support to better format output

refs #2137
Fixed not checking whether compression params are NULL.
Inserting node owners into temporary search tree.

- Was causing wrong node->owner->node values and thus incomplete
  additional sections.