Revert removal of XENFORO enum, hash class and custom SQL

- Undo commits 121d323 and 1c12278
- Add TODO's with issue number
- Add slight, necessary adjustments for code changes since the reverted commits

src/main/java/fr/xephi/authme/security/HashAlgorithm.java

@@ -36,6 +36,7 @@ public enum HashAlgorithm {
     WHIRLPOOL(fr.xephi.authme.security.crypts.WHIRLPOOL.class),
     WORDPRESS(fr.xephi.authme.security.crypts.WORDPRESS.class),
     XAUTH(fr.xephi.authme.security.crypts.XAUTH.class),
+    XENFORO(fr.xephi.authme.security.crypts.XF.class),
     CUSTOM(null);
 
     private final Class<? extends EncryptionMethod> clazz;