Rrset Free Remove

I'm not sure if this will conflict with some of your work, if yes. we'll cancel this.

- nodes were marked as empty, but the information was never used ...
- renamed one function for clarity.

Fixes #218

Log Control

refs #222

DDNS tests for new test suite

Include config.h

The config.h is now implicitly included using -include option of the
compiler. After this change, config.h need not be placed at the first
position in all source files.

Conflicts:
	src/knot/server/xfr-handler.c

Conf Optimization

Auto Retransfer

refs #220

*14.102.145.in-addr.arpa. is valid dname (no wildcard!) but evident typo

refs #220

 - random test used for chain fix testing
 - manual test, some of the cases copied from the old tests, but not all.

Signing after UPDATE fixed

Fixed changeset signing after UPDATE.

Was ignoring RRSIGs related to a RRSet that was completely removed. This was a relict of old code when RRSIGs were connected to their RRSets.

Also simplified the function (and function `sign_rr_should_be_signed()`) and did some minor refactoring and polishing. Please try to check if function `sign_changeset_wrap()` is equivalent to its previous state.

Revert NSEC chain fixes due to excessive complexity of the code.