contrib: move print and tolower from internal

Knot.files

src/Makefile.am

src/contrib/print.c

src/contrib/print.h

src/contrib/tolower.h

src/knot/nameserver/axfr.c

src/knot/nameserver/ixfr.c

src/knot/nameserver/update.c

src/libknot/dname.c

src/libknot/internal/tolower.c

src/libknot/packet/compr.c

src/libknot/rrtype/nsec3.c

src/utils/common/exec.c

src/utils/kdig/kdig_exec.c