libknot unified

This MR removes extra shared libknot-* libraries from distribution.

There are now only three libraries visible to the public:
libknot
libdnssec
libzscanner

Due to the cross-use of libknot-internal from libknotd and libknotus, some code might be linked twice, but it's inevitable unless we want to expose volatile API/ABI to the outside world.

The few more things:
- Removed all _public_ declarations from internal/* and yparser/*
- Add #include libknot/internal/macros.h to internal/* and yparser/* (as a side effect from playing with symbol visibility)
- Fixed library versioning and bumped libknot from SOVERSION 0 to 1, since some symbols have disappered since (due to visibility)

See merge request !379

Don't run clean target in parallel as running 'make -j8 clean check' would have some interesting results if check was ran in parallel with clean

Tidy up libdnssec.pc, we don't expose neither GnuTLS nor jansson symbols outside, so everything should be in .private

Tidy up libknot.pc - we don't expose any symbols from linked libraries, so everything should be in .private

Add more debug output for used _CFLAGS and _LIBS to configure and explicitly link knotd with $(liburcu_LIBS)

Remove version-script support to remove additional complexity it introduces (it's not really needed when we hide internal symbols)

Make internal and yparser convenient libraries (noinst_LTLIBRARIES)
and link them only where needed.  Some of the code will get linked
twice into the binary, but that's inevitable unless we want to keep
exporting volatile symbols library to the outside world.

(Or we can cleanup usage of libknot-internal outside libknot and perhaps libknotd.)

Merge libknot-int and libknot-yparser into libknot with versioned symbols to separate main KNOT library and INTERNAL+YPARSER

1. libknot - interfaces has been added (0:0:0 -> 1:0:1)
2. libzscanner - source change, but interface has not (0:1:0)
3. libdnssec - new library (0:0:0)
4. libknot-int - new library (0:0:0)
5. libknot-yparser - new library (0:0:0)

Completion scripts for Bash and ZSH.

Closes #353

knot1to2: build with daemon, install to libexec

See merge request !377

- Debian: assume current version is Jessie
- Arch, Gentoo: add installation command instead of a link
- FreeBSD: install from root shell, sudo is not in default installation

- Add 'highlight' option to set default syntax on each page
- Add 'code-block' for exceptions