Remove redundant and unused message

- Remove 'reg_voluntarily'
- Remove 'user_unknown' in favor of 'unknown_user' - but move text from old 'user_unknown' to 'unknown_user'

Found by @Twonox

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

@@ -56,7 +56,7 @@ public class AccountsCommand implements ExecutableCommand {
 
                     List<String> accountList = dataSource.getAllAuthsByIp(auth.getIp());
                     if (accountList.isEmpty()) {
-                        commonService.send(sender, MessageKey.USER_NOT_REGISTERED);
+                        commonService.send(sender, MessageKey.UNKNOWN_USER);
                     } else if (accountList.size() == 1) {
                         sender.sendMessage("[AuthMe] " + playerName + " is a single account player");
                     } else {

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

@@ -29,7 +29,7 @@ public class LastLoginCommand implements ExecutableCommand {
 
         PlayerAuth auth = dataSource.getAuth(playerName);
         if (auth == null) {
-            commonService.send(sender, MessageKey.USER_NOT_REGISTERED);
+            commonService.send(sender, MessageKey.UNKNOWN_USER);
             return;
         }
 

src/main/java/fr/xephi/authme/message/MessageKey.java

@@ -26,9 +26,6 @@ public enum MessageKey {
     /** You're not logged in! */
     NOT_LOGGED_IN("not_logged_in"),
 
-    /** You can register yourself to the server with the command "/register <password> <ConfirmPassword>" */
-    REGISTER_VOLUNTARILY("reg_voluntarily"),
-
     /** Usage: /login <password> */
     USAGE_LOGIN("usage_log"),
 
@@ -77,9 +74,6 @@ public enum MessageKey {
     /** Password changed successfully! */
     PASSWORD_CHANGED_SUCCESS("pwd_changed"),
 
-    /** This user isn't registered! */
-    USER_NOT_REGISTERED("user_unknown"),
-
     /** Passwords didn't match, check them again! */
     PASSWORD_MATCH_ERROR("password_error"),
 

src/main/java/fr/xephi/authme/process/login/AsynchronousLogin.java

@@ -117,7 +117,7 @@ public class AsynchronousLogin implements AsynchronousProcess {
 
         PlayerAuth auth = dataSource.getAuth(name);
         if (auth == null) {
-            service.send(player, MessageKey.USER_NOT_REGISTERED);
+            service.send(player, MessageKey.UNKNOWN_USER);
             // Recreate the message task to immediately send the message again as response
             // and to make sure we send the right register message (password vs. email registration)
             limboPlayerTaskManager.registerMessageTask(name, false);