RDATA lowercase: Dnames to lc when adding to zone.
tests-extra: DNSSEC + mixed cases in RDATA dnames

- no_resign extended to test whether the zone will be resigned
  if only the case of RDATA dname changes.
- Added new DNSSEC test to sign zone with wierd records.
RDATA lowercase: Removed redundant comments.
Merge branch 'master' into lowercase
tests-extra: Duplicate RDATA differing only in case
Merge branch 'master' into lowercase
RDATA lowercase: Converting in packet parsing + zone load.

Converting to lowercase when saving to zone proved insufficient,
because case-insensitive comparison of RDATA would be needed in some
scenarios - e.g. in IXFR (SOA replacement) and DDNS processing.

Moved the conversion to packet parsing - all dnames in RDATA
are converted to lowercase when parsed from wire. RDATA parsed
from zone file are converted there (in scanner_process()). Later
the conversion may be moved to a lower level of parsing (and with
some option to turn it on/off).

QNAME is unaffected by this change.
RDATA lowercase: Removed unnecessary conversions
tests-extra: Different origin case in records zone
Merge branch 'master' into lowercase

Conflicts:
	src/knot/dnssec/nsec3-chain.c
naptr: fix compile warning (missing const)
lowercase: Unified to one function + type check.

Only RFC 4034 types are converted to lowercase.
Unified the conversion to one RRSet function used in both zone
parsing and packet parsing.
lowercase: Empty RDATA check.
lowercase: dname lookup format in lowercase.
lowercase: ci comparison in NSEC chain fixing.
Merge branch 'master' into lowercase

Conflicts:
	Knot.files
lowercase: Missing doxygen + Some MR fixes.

- Semantic check: missing conversion of next NSEC to lowercase
  when comparing with apex.
- Changed condition when SERVFAIL is returned (no combination
  with any possible Ext RCODE).
lowercase: Improved 'no resign' test.

- Test changing case in different types and even adding a duplicate
  record that differs only in lettercase in RDATA.
- Also, test changing case in NSEC's next domain name. Should result
  in resign, but that doesn't happen right now.
tests-extra: no_resign: added missing file + test cleanup
Merge branch 'master' into lowercase