Contextual Object Entry

This addresses issues we've been experiencing on TTR because clients expect OTP-style interest operation behavior. For example, the GET_ZONES_COUNT_RESP sent to the CA would be 3, for an NPC and two doors. However, I believe the CA will actually end up receiving 4 OBJECT_ENTER_LOCATIONs, meaning that CLIENT_DONE_INTEREST would be sent early, causing clients to not have all the objects generated that they expected.

This is basically an implementation of https://github.com/Astron/Astron/wiki/%5BArch%5D-Implementing-Interests#proposal-1
This comment is out of date with the following `self.expectNone(client)`

I guess something like `# The client shouldn't be informed about the entry yet`