thread-safe crypto: add module with initialization and cleanup

src/Makefile.am

src/knot/main.c

src/knot/server/server.c

src/knot/server/tcp-handler.c

src/knot/server/udp-handler.c

src/knot/server/zone-load.c

src/libknot/dnssec/crypto.c

src/libknot/dnssec/crypto.h

src/utils/nsec3hash/nsec3hash_main.c

src/utils/nsupdate/nsupdate_main.c

tests/dnssec_sign.c