More aspects of the cluster configuration to get fleshed out later,
but a basic cluster like one would use for a live deployment
can now be instantiated and run under supervision. The new
clusterized-pcap-processing supervisor mode is also not done yet.
For backward compatibility when reading values, we first check
the ZEEK-prefixed value, and if not set, then check the corresponding
BRO-prefixed value.
* All "Broxygen" usages have been replaced in
code, documentation, filenames, etc.
* Sphinx roles/directives like ":bro:see" are now ":zeek:see"
* The "--broxygen" command-line option is now "--zeexygen"
