OTP : Improve : tighten the security + cosmetic

set double authentication : create, send link, usable with
FreeOTP (opensource) AEgis (opensource) and Google Authenticator

1. OTP : prevent direct access without going throught the 2FA mechanism
2. Go back to the url where you were disconnected
3. Cosmetic

html/ajax_misc.php

@@ -96,7 +96,12 @@ else
     $g_user = new Noalyss_user($cn);
     $g_user->check(true);
 }
-
+/**
+ * check if 2FA is completed
+ */
+if ( ! $g_user->is_double_identified()) {
+   exit();
+}
 IDate::set_firstDate($g_user->get_first_week_day());
 ITva_Popup::set_vat_code($g_user->get_vat_code_preference());