Start working on the changepassword api method

TODO: fix unit testing

src/main/java/fr/xephi/authme/api/v3/AuthMeApi.java

@@ -285,6 +285,16 @@ public class AuthMeApi {
         management.performUnregisterByAdmin(null, name, Bukkit.getPlayer(name));
     }
 
+    /**
+     * Change a user's password
+     *
+     * @param name the user name
+     * @param newPassword the new password
+     */
+    public void changePassword(String name, String newPassword) {
+        management.performPasswordChangeAsAdmin(null, name, newPassword);
+    }
+
     /**
      * Get all the registered names (lowercase)
      *