Commit refs #927, #928.

Commit refs #927, #928, #935.

* Fast in-memory lookup.
* ACID traits.
* Fragmentation trimming.

Commit refs #925, #927, #928, #935.

- Replacing RRSet owner directly in zone_add_rrset().
- Fixed check if owner in RRSets should be replaced in
  dnames_from_node_to_table().
- Fixed check for return value from dname_table_add_dname2()
  in dnames_from_rdata_to_table().

Zone compiler does not work well. Don't know if it is because of
my changes to the zone and node API.

- Fixed wrong check if the RRSet's owner should be replaced.
- zone_add_rrset() now also finds the node where to insert it.
  (Maybe not needed).
- Modified AXFR-in packet processing to properly insert RRSets
  into zone.

refs #920 1h

- Divided dnames_from_node_to_table() to smaller functions
  (for RRSet and RDATA).
- Added add_rrset() function.
- Added new error code.

refs #920 @1h

refs #920 @5m

- Function for saving zone.
- Function for finding zone in config.
- Function for finding temp name for the zone files.
- Functions for saving to text and binary files.
- Header of function for switching zone in nameserver (not
  implemented).

- Saving to binary database does not work yet,

refs #875 @30m, #786 @1h, #785 @1h

refs #920 @1h

refs #920 @20m

- zone_add_node() now creates parent nodes on demand.
- Modified all calls to zone_add_node().
- Creating dname table in zone_new().
- Argument checking in dname_table_find_dname().

refs #875 @1h20m

- Properly creating new nodes.
- Properly replacing RR owner.
- Returning positive value when the transfer is finished.

refs #875 @2h

- Adding RRs to nodes (and merging if needed).
- Special handling of first node in zone.
- Adding nodes to zone.

TODO:
 - Does not finish properly when the transfer is finished
   (distinguish using the SOA record).
 - Does not set parents to the nodes (do it during adjusting).

refs #875 @1h

refs #875 @15m

refs #875 @20m

Refs #878 @1h

Fixes #885 @20m

Conflicts:
	Knot.files
	src/Makefile.am
	src/dnslib/zone.c
	src/dnslib/zone.h
	src/knot/server/name-server.c

Conflicts:
	samples/example.com.zone
	src/Makefile.am
	src/dnslib/dnslib-error.c
	src/dnslib/error.h

Conflicts:
	src/dnslib/zone.c