knsupdate: error message if the key cannot be processed

closes #2377
Moved RRSet unit tests to proper directory.

- Changed paths in Knot.file, Makefile.am and in the test files.
Do not convert DNAMEs to special format for trie.
Fixed wrong if - do not insert DNAMEs to trie, if there are already inside.
Enabled duplicate checking in AXFR bootstraps.
Fixed wrong switching of free'd DNAMEs in XFR-in.

- Names were not actually switched, which lead to memory errors.
- Changed API in some RRSet functions accordingly.
nsupdate: do not append origin to added records

closes #2378