Expose way to clear history from MessageHistory

* We don't necessarily want to always call ClearAll when using
  MessageHistory since it also removes the MessageTrackListener from
  each of the IMessagingHubs.
* Expose ClearHistory (previously a private method called clearData)
Remove pak-Data.zip from Bottles.Docs csproj

* File doesn't exist and isn't needed anymore
Merge pull request #102 from DarthFubuMVC/MessageHistoryFix

Message history fix