#1141 Move TOTP code during login as separate step: /2fa code

Rough version.
- Introduces a limbo player state on the LimboPlayer, allowing us to add further mandatory actions between successful (password) authentication and the ability to play on the server

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

@@ -197,6 +197,9 @@ public enum MessageKey {
     /** Your secret code is %code. You can scan it from here %url */
     TWO_FACTOR_CREATE("misc.two_factor_create", "%code", "%url"),
 
+    /** Please submit your two-factor authentication code with /2fa code &ltcode>. */
+    TWO_FACTOR_CODE_REQUIRED("two_factor.code_required"),
+
     /** You are not the owner of this account. Please choose another name! */
     NOT_OWNER_ERROR("on_join_validation.not_owner_error"),
 

src/main/java/fr/xephi/authme/message/updater/MessageUpdater.java

@@ -131,6 +131,7 @@ public class MessageUpdater {
             .put("captcha", new String[]{"Captcha"})
             .put("verification", new String[]{"Verification code"})
             .put("time", new String[]{"Time units"})
+            .put("two_factor", new String[]{"Two-factor authentication"})
             .build();
 
         Set<String> addedKeys = new HashSet<>();