dumpInfo prints all config set on an entity, not just those matching explicit keys
more flexibility in MapConfigKey and SetConfigKey - if you set a map or set against the StructuredConfigKey it is used as a base,
and all subkeys are put on top of that; also any key matching a.map.subkey=1 is treated as a subkey if we access a.map as a map
(it does not *have* to be a sub element config key)

this allows us to set map and set configs in yaml
add (now working) vm provisioning properties for cassandra
(and a quick check to ensure classpath is sensible when running)