Migrated Search to keep actual topics + categories on children.

* Added DOT-based supervisor tree viewing with DebugActor
* Moved Topic/Category actors to be their own beings
* Moved splitting into its own actor.  While splitting, Topic nodes can still respond to queries.
* Startup still has timeing issues:  I.e. tree is not loaded immediately.
* `NodeManager` now knows how to alter the state of a node in the search index.  All node creation and
  storage should go through him.
* Can no longer save additional hotels in topics, will work on this shortly.