tests: DDNS response signatures checking

See merge request !264

Conflicts:
	src/libknot/errcode.c

systemd journal logging support

closes #273

See merge request !262

refs #273

refs #273

refs #273

knotc: remote messages

See merge request !261

The response should fit into a TCP DNS message.

Nsec3 test

See merge request !259

The new DNSSEC code expects one functional KSK and ZSK for each
algoritm. Otherwise, an error is reported and signing fails.

DNSSEC: constraint checks for KSK and ZSK

fixes #285

See merge request !256

TSIG+OPT bugfixes

See merge request !257

fixes #282

Bulk updates

Pending:
 - ~~renaming (update vs. request vs. query ...)~~
 - ~~proper logging (waiting for !250)~~
 - ~~`rrset_is_nsec3_rel()` and `mm_realloc` copypasta~~
 - partial zone adjustment - next MR

Pros:
 - faster for lots of small updates
 - improved terrible empty node cleanup (now takes time proportional to size of update, not size of the zone)
 - spinlocks instead of mutexes for ddns q access (faster for this case + less memory :fisted_hand_sign: )

Cons:
 - if one transfer fails (no matter the reason, except for acl issues), they all fail
 - might actually be slower for small singular updates, but oh well

Not sure if good or bad:
 - most of logging is lost (only logs errors in detail, i.e. who sent the faulty update)

See merge request !251