Add per-arena setting announcer-type.

Introduces the concept of an Announcer, which is invoked whenever the
`announce` methods on the Arena interface are invoked. Previously, all
announcements would simply be sent to the arena's Messenger, but this
new feature allows us to move them up into titles to help declutter the
somewhat overloaded chat box.

By default, to help people discover the new feature, the announcer type
is `title`, but it is possible to switch back to `chat` for the original
behavior.

Closes #272

src/main/java/com/garbagemule/MobArena/ArenaImpl.java

@@ -3,6 +3,9 @@ package com.garbagemule.MobArena;
 import static com.garbagemule.MobArena.util.config.ConfigUtils.makeSection;
 
 import com.garbagemule.MobArena.ScoreboardManager.NullScoreboardManager;
+import com.garbagemule.MobArena.announce.Announcer;
+import com.garbagemule.MobArena.announce.MessengerAnnouncer;
+import com.garbagemule.MobArena.announce.TitleAnnouncer;
 import com.garbagemule.MobArena.steps.Step;
 import com.garbagemule.MobArena.steps.StepFactory;
 import com.garbagemule.MobArena.steps.PlayerJoinArena;
@@ -75,6 +78,7 @@ public class ArenaImpl implements Arena
     private String name;
     private World world;
     private Messenger messenger;
+    private Announcer announcer;
 
     // Settings section of the config-file for this arena.
     private ConfigurationSection settings;
@@ -232,6 +236,16 @@ public class ArenaImpl implements Arena
         String prefix = settings.getString("prefix", "");
         this.messenger = !prefix.isEmpty() ? new Messenger(prefix) : plugin.getGlobalMessenger();
 
+        // Announcer
+        String announcerType = settings.getString("announcer-type", "chat");
+        if (announcerType.equals("chat")) {
+            announcer = new MessengerAnnouncer(this.messenger);
+        } else if (announcerType.equals("title")) {
+            announcer = new TitleAnnouncer(5, 60, 10);
+        } else {
+            throw new ConfigError("Unsupported announcer type: " + announcerType);
+        }
+
         // Actions
         this.histories = new HashMap<>();
         this.playerJoinArena = PlayerJoinArena.create(this);
@@ -454,7 +468,7 @@ public class ArenaImpl implements Arena
     @Override
     public void announce(String msg) {
         for (Player p : getAllPlayers()) {
-            messenger.tell(p, msg);
+            announcer.announce(p, msg);
         }
     }
 

src/main/java/com/garbagemule/MobArena/announce/Announcer.java

@@ -0,0 +1,15 @@
+package com.garbagemule.MobArena.announce;
+
+import org.bukkit.entity.Player;
+
+public interface Announcer {
+
+    /**
+     * Announce the given message to the given player.
+     *
+     * @param player a player to send a message to, non-null
+     * @param message the message to send, non-null
+     */
+    void announce(Player player, String message);
+
+}

src/main/java/com/garbagemule/MobArena/announce/MessengerAnnouncer.java

@@ -0,0 +1,19 @@
+package com.garbagemule.MobArena.announce;
+
+import com.garbagemule.MobArena.Messenger;
+import org.bukkit.entity.Player;
+
+public class MessengerAnnouncer implements Announcer {
+
+    private final Messenger messenger;
+
+    public MessengerAnnouncer(Messenger messenger) {
+        this.messenger = messenger;
+    }
+
+    @Override
+    public void announce(Player player, String message) {
+        messenger.tell(player, message);
+    }
+
+}

src/main/java/com/garbagemule/MobArena/announce/TitleAnnouncer.java

@@ -0,0 +1,22 @@
+package com.garbagemule.MobArena.announce;
+
+import org.bukkit.entity.Player;
+
+public class TitleAnnouncer implements Announcer {
+
+    private final int fadeIn;
+    private final int stay;
+    private final int fadeOut;
+
+    public TitleAnnouncer(int fadeIn, int stay, int fadeOut) {
+        this.fadeIn = fadeIn;
+        this.stay = stay;
+        this.fadeOut = fadeOut;
+    }
+
+    @Override
+    public void announce(Player player, String message) {
+        player.sendTitle("", message, fadeIn, stay, fadeOut);
+    }
+
+}