* support LookupReferencesManager registration of namespaced lookup and eliminate static configurations for lookup from namespecd lookup extensions
- druid-namespace-lookup and druid-kafka-extraction-namespace are modified
- However, druid-namespace-lookup still has configuration about ON/OFF
HEAP cache manager selection, which is not namespace wide
configuration but node wide configuration as multiple namespace shares
the same cache manager
* update KafkaExtractionNamespaceTest to reflect argument signature changes
* Add more synchronization functionality to NamespaceLookupExtractorFactory
* Remove old way of using extraction namespaces
* resolve compile error by supporting LookupIntrospectHandler
* Remove kafka lookups
* Remove unused stuff
* Fix start and stop behavior to be consistent with new javadocs
* Remove unused strings
* Add timeout option
* Address comments on configurations and improve docs
* Add more options and update hash key and replaces
* Move monitoring to the overriding classes
* Add better start/stop logging
* Remove old docs about namespace names
* Fix bad comma
* Add `@JsonIgnore` to lookup factory
* Address code review comments
* Remove ExtractionNamespace from module json registration
* Fix problems with naming and initialization. Add tests
* Optimize imports / reformat
* Fix future not being properly cancelled on failed initial scheduling
* Fix delete returns
* Add more docs about whole introspection
* Add `/version` introspection point for lookups
* Add more tests and address comments
* Add StaticMap extraction namespace for testing. Also add a bunch of tests
* Move cache system property to `druid.lookup.namespace.cache.type`
* Make VERSION lower case
* Change poll period to 0ms for StaticMap
* Move cache key to bytebuffer
* Change hashCode and equals on static map extraction fn
* Add more comments on StaticMap
* Address comments
* Make scheduleAndWait use a latch
* Sanity renames and fix imports
* Remove extra info in docs
* Fix review comments
* Strengthen failure on start from warn to error
* Address comments
* Rename namespace-lookup to lookups-cached-global
* Fix injective mis-naming
* Also add serde test
Charles Allen