Fix getOnlinePlayers call to support all versions

Moved IPlayerDataManager from api module to common module - it is not part of the API as there is no supported way to obtain an instance of it.

common/src/main/java/com/lishid/openinv/internal/IPlayerDataManager.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2011-2014 lishid.  All rights reserved.
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation,  version 3.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.lishid.openinv.internal;
+
+import java.util.Collection;
+
+import org.bukkit.OfflinePlayer;
+import org.bukkit.entity.Player;
+
+public interface IPlayerDataManager {
+
+    /**
+     * Loads a Player for an OfflinePlayer.
+     * </p>
+     * This method is potentially blocking, and should not be called on the main thread.
+     * 
+     * @param offline
+     * @return
+     */
+    public Player loadPlayer(OfflinePlayer offline);
+
+    /**
+     * Gets a unique identifying string for an OfflinePlayer.
+     * 
+     * @param player
+     * @return
+     */
+    public String getPlayerDataID(OfflinePlayer player);
+
+    /**
+     * Gets an OfflinePlayer by the given unique identifier.
+     * 
+     * @param identifier the unique identifier
+     * @return the OfflinePlayer, or null if no exact match was found
+     */
+    public OfflinePlayer getPlayerByID(String identifier);
+
+    /**
+     * Gets a Collection of all Players currently online.
+     * 
+     * @return the Collection of Players
+     */
+    public Collection<? extends Player> getOnlinePlayers();
+
+}