Fix several bugs

These are:
- not immediately updating ChatScene if a contact was blocked and both
are online
- ContactSearchTab showing previously entered text on reopening (without
showing suggestions)
- users not getting notified if someone else blocked them while they
were offline
- no logger statements in UserUtil

Still to do:
- Move ContextMenu from chatList to ChatControl
- Test behavior for groups

client/src/main/java/envoy/client/ui/controller/ContactSearchTab.java

@@ -124,5 +124,8 @@ public class ContactSearchTab implements EventListener {
 	}
 
 	@FXML
-	private void backButtonClicked() { eventBus.dispatch(new BackEvent()); }
+	private void backButtonClicked() {
+		searchBar.setText("");
+		eventBus.dispatch(new BackEvent());
+	}
 }