Adaptive question behaviour for CodeRunner questions.

This Moodle question behaviour was created by Richard Lobb, University of Canterbury, New Zealand.

This question behaviour was created solely for use with CodeRunner: https://github.com/trampgeek/moodle-qtype_coderunner/. It provides the caching of question test results needed to prevent re-testing a student's code every time the result page is viewed.

This version (v1.3.9) passes information about the current attempt step to the question's grader, such as the number of checks and prechecks, the current mark and the preferred behaviour originally selected (e.g. for a quiz in which the question is being used). This allows a CodeRunner question author to provide more customised feedback, e.g. when using a combinator template grader.