numerical and shortanswer question types: problems with compare_responses and test_re...

numerical and shortanswer question types: problems with compare_responses and test_response.

MDL-15315 The previous fix for this issue with wildcard answers in the item analysis report caused the following two regressions. This patch fixes it properly.

MDL-17247 This is basiclly pointing out the weridness in the previous fix and gave some useful clues as to a proper solution. Thanks Oleg.

MDL-17610 This was a report of a problem with each attempt builds on last, with a shortanswer question, where the sutdent's response contains a '.

Also, lots of unit tests to try to ensure the new code is right.