Fix #316 Ordinary player can use /authme unregister

- Change wrong player permissions to admin permissions
- Rename command class names that were the same for the ordinary vs. admin task
- Create test to ensure that commands with OP_ONLY default require an admin permission node

src/main/java/fr/xephi/authme/command/executable/authme/ChangePasswordAdminCommand.java

@@ -18,7 +18,7 @@ import java.security.NoSuchAlgorithmException;
 /**
  * Admin command for changing a player's password.
  */
-public class ChangePasswordCommand extends ExecutableCommand {
+public class ChangePasswordAdminCommand extends ExecutableCommand {
 
     @Override
     public boolean executeCommand(final CommandSender sender, CommandParts commandReference, CommandParts commandArguments) {

src/main/java/fr/xephi/authme/command/executable/authme/RegisterAdminCommand.java

@@ -15,8 +15,9 @@ import org.bukkit.command.CommandSender;
 import java.security.NoSuchAlgorithmException;
 
 /**
+ * Admin command to register a user.
  */
-public class RegisterCommand extends ExecutableCommand {
+public class RegisterAdminCommand extends ExecutableCommand {
 
     /**
      * Execute the command.

src/main/java/fr/xephi/authme/command/executable/authme/UnregisterAdminCommand.java

@@ -21,8 +21,9 @@ import org.bukkit.scheduler.BukkitScheduler;
 import org.bukkit.scheduler.BukkitTask;
 
 /**
+ * Admin command to unregister a player.
  */
-public class UnregisterCommand extends ExecutableCommand {
+public class UnregisterAdminCommand extends ExecutableCommand {
 
     /**
      * Execute the command.