Mention scylla-tools-java and scylla-jmx in HACKING.md
Mention scylla-tools-java and scylla-jmx in HACKING.md

I struggled a bit finding out why nodetool was not working, so it
might be a good idea to expand the documentation a bit.

Signed-off-by: Rafael Ávila de Espíndola <1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>
Message-Id: <20181120233358.25859-1-1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,avikivity/scylla