v2.0.0.4

UI - Fix a (phase 3 only) issue where the transaction list sometimes displaying unnecessary duplicate "rejected" earning messages for every valid earning message.
RPC - Add two commands disablewitnessing/enablewitnessing - useful for various testing scenarios and some other fringe use cases.
NET - Fix an annoying instability issue (crash) in the networking code that is triggered by the checkpoint system in some scenarios.