refs #2027 @1h

refs #2027 @30m

refs #2027 @4h

- RRSets were not added when there was nothing to merge.

- knot_node_add_rrset was never called with merge option -> changed to knot_add_rrset_no_merge
- add_rrset_no_dupl -> add_rrset (was wrongly changed when replacing tree for array)

Conflicts:
	src/libknot/rrset.c

- Compression information can be present, some DNAMEs are not comprimable.

- Explicit DNAME handling was not needed.
- Cleaned up the file a bit.

If the ragel isn't found, use echo command instead of blank variable.

- Removed unused API function.

- Introduced in b2c7071c

- Removed some commented code.

- Was showing free'd data.

- In DDNS, SOA RRs are not copied with RDATA DNAMEs - double free when freeing changesets
- Could produce a leak somewhere! (ixfr-in)

- Would cause crash when removing RR from non-existent nodes.

refs @2138

refs @2138

refs #2027 @1h

Conflicts:
	src/Makefile.am
	src/libknot/rdata.c
	src/libknot/rrset.c
	src/libknot/util/descriptor.h
	src/libknot/zone/zone-contents.c
	src/zcompile/parser-descriptor.c