common: Discarded the libknots (common-knot) library.

Most of the files were moved to knot/common/ (ex knot/other/).

Two files moved to utils, because were used only there
(hex, strtonum).

One file (strlcat) moved to libknot/internal/, as it was used both
in server and in libknot. (Also, strlcpy was there already).
Moved heap to libknot.
Moved some forgotten files properly to libknotcs
Updated project file
Merge branch 'remove-common' into 'master'

Discarded the libknots (common-knot) library

Most of the files were moved to `knot/common/` (ex `knot/other/`).

Two things moved to `utils/common`, because were used only there (`hex`, `strtonum`).

One file (`strlcat`) moved to `libknot/internal/`, as it was used both in server and in libknot. (Also, `strlcpy` was there already).

See merge request !306