Add converting framework as well as the converter for Backpack

Adds command /pvconvert <all | plugin name>
Adds permission playervaults.convert
Adds Converter interface for future converters
Adds BackpackConverter - A converter for Backpack
(http://dev.bukkit.org/bukkit-plugins/backpack/)

src/main/java/com/drtshock/playervaults/converters/Converter.java

@@ -0,0 +1,34 @@
+package com.drtshock.playervaults.converters;
+
+/**
+ * Represents a simple converter for converting another plugin's content
+ * to PlayerVaults.
+ *
+ * @author turt2live
+ */
+public interface Converter {
+
+    /**
+     * Converts the other plugin's data.
+     *
+     * @return the number of vaults converted. Returns 0 on none converted
+     * or -1 if no vaults were converted.
+     */
+    public int doConvert();
+
+    /**
+     * Determines if this converter is applicable for converting to PlayerVaults.
+     * This may check for the existance of a plugin, plugin folder, or otherwise.
+     *
+     * @return true if this converter can convert, false otherwise
+     */
+    public boolean canConvert();
+
+    /**
+     * Gets the name of this converter
+     *
+     * @return the converter name
+     */
+    public String getName();
+
+}