MDL-8003 - part - Use formslib for question editing forms

This commit does two things:
1. Gives question types he opion to use formslib for their editing forms, instead of the old mechanism.
2. Converts the truefalse question type to formslib.

question/edit.php

@@ -31,6 +31,7 @@
     require_login($course->id, false);
   
     $SESSION->returnurl = $FULLME;
+    $SESSION->fromurl = $FULLME;
 
     // Print basic page layout.