MessagingService should be able deliver local messages (messages to self) without using a network interface.

At the moment, in various places in the code, there are special code paths for local message handling. It usually looks like this:

if (replica.isSelf)
  // deal with the message locally by manually invoking a handling method
else
  messagingService.send(...)

This pattern is error-prone, as failing to recognize local messages results in pushing them through a local network interface. This may introduce a significant performance penalty.
It also makes understanding the code harder, as there are two separate code paths for message handling (local path and IVerbHandler).

Instead, MessagingService should pass local messages directly to the appropriate IVerbHandler. Once this is done, all the `if (replica.isSelf) ... else ...` occurrences could be refactored to simply calling `messagingService.send(...)`. This would move message handling logic into a single place (IVerbHandler).