Add back buffer entries based on events.

Any formattable DisplayableEvent received on a frame container's
event bus is now automatically added to the IRC Document.

Current problems:
  1) Every time this happens the old path still executes, so you
     end up with two lines
  2) Every event on a channel's event bus gets passed to the
     server's, so the lines appear there as well.

src/com/dmdirc/events/DisplayableEvent.java

      */
     <T> Optional<T> getDisplayProperty(DisplayProperty<T> property);
 
+    /**
+     * Gets the timestamp at which the event occurred.
+     *
+     * @return The timestamp the event occurred at.
+     */
+    long getTimestamp();
+
 }

src/com/dmdirc/ui/core/BackBuffer.java

 import com.dmdirc.DMDircMBassador;
 import com.dmdirc.FrameContainer;
 import com.dmdirc.events.DisplayableEvent;
+import com.dmdirc.interfaces.config.AggregateConfigProvider;
 import com.dmdirc.ui.messages.ColourManagerFactory;
 import com.dmdirc.ui.messages.EventFormatter;
+import com.dmdirc.ui.messages.Formatter;
 import com.dmdirc.ui.messages.IRCDocument;
 import com.dmdirc.ui.messages.Styliser;
 
+import java.util.Date;
+
+import net.engio.mbassy.listener.Handler;
+
 /**
  * Models the history of a window in the client.
  */
     private final Styliser styliser;
     private final DMDircMBassador eventBus;
     private final EventFormatter formatter;
+    private final AggregateConfigProvider configProvider;
 
     public BackBuffer(
             final FrameContainer owner,
         this.document = new IRCDocument(owner.getConfigManager(), styliser, owner.getEventBus());
         this.eventBus = owner.getEventBus();
         this.formatter = formatter;
+        this.configProvider = owner.getConfigManager();
     }
 
     /**
      *
      * @param event The event to be displayed.
      */
+    @Handler
     public void handleDisplayableEvent(final DisplayableEvent event) {
+        formatter.format(event)
+                .map(l -> new String[]{getTimestamp(event), l})
+                .ifPresent(document::addText);
+    }
 
+    private String getTimestamp(final DisplayableEvent event) {
+        return Formatter.formatMessage(configProvider, "timestamp",
+                new Date(event.getTimestamp()));
     }
 
     public IRCDocument getDocument() {

src/com/dmdirc/ui/messages/IRCDocument.java

         }
         fireRepaintNeeded();
     }
-
 }