#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/data/limbo/LimboPlayerState.java

@@ -0,0 +1,11 @@
+package fr.xephi.authme.data.limbo;
+
+public enum LimboPlayerState {
+
+    PASSWORD_REQUIRED,
+
+    TOTP_REQUIRED,
+
+    FINISHED
+
+}