Adaptive for external grading

question behaviour for questions that are automatically graded by a grading back-end, especially stores the grader feedback for display.
Used for qtype_proforma.
This question behaviour is designed to be used by the ProFormA question type plugin.
It is derived from the adaptive question behaviour and adds the
following features:
store extra grading information (feedback from grader)
avoid regrading when finishing an attempt
special handling for internal grading errors
optional adaptivenopenalty behaviour