extended form-fields autocorrection handling - added functionality of per-form-field statistics - added support for "radio"/single choice test items - added support for richtext handling in "radio" - added a (limited) method to set a form-field to a correct value, based on "correct_when". So far, just a minimal set of predicated is handled - improved "unknown" handling, when the code does not know, whether item is correct or not - refactored some code - improved source code documentation