Add xAPI result support on mod_h5pactivity

All new classes are covered by PHPunitests:

vendor/bin/phpunit -c mod/h5pactivity/

Manual Testing 1 (activity creation form)

1. Create a course and a user and enrol it as student
2. Activate edition in the course and create a new H5P activity. One in the form:
   1. Set the activity name to "H5P quiz"
   2. In "Package File" upload the provided H5P (file: question-set-616.h5p)
   3. Expand "Grade and "Attempt" configurations
      1. Check that Grade "type" is set to "Point" by default
      2. Check that Attempts options "Enable attempt tracking" is enabled by default
      3. Check that Attempt grading method is set to "highest attempt" by default
   4. Change grade "type" to "none"
      1. Check that "Attempt grading method" gets disabled
   5. Change grade "type" to "scale"
      1. Check that "Attempt grading method" still disabled
   6. Set again grade "type" to "point"
      1. Check that "Attempt grading method" get enabled again
   7. Set "Enable attempt tracking" to No
      1. Check that "Attempt grading method" disappears
   8. Put again "Enable attempt tracking" to Yes
      1. Check that "Attempt grading method" appears
   9. Click on "Save and display"
3. Check that the H5P content appears like the image

Manual Testing 2 (Point highest grading)

1. Login as a student and go to the H5P activity created in the previous test.
2. Access the H5P activity and do one attempt with this answers:
   1. Which of the berries listed below are berries you can pick in the wild? check "Halle Berry" and "Cocktail cherry"
   2. Drag and drop: from left to right drag the first image to "Blueberry", the second to "Redcurrant" ans the third to "Cloudberry" (like the image attached   )
   3. Which one of the following berries are red? select "Cranberries"
   4. Click on "Finish" button.
   5. Check that your result is 2/6 and a message "Oh, no! This didn't go so well" appears.
3. Click on the "Retry" button to start a new attempt with the following answers:
   1. Which of the berries listed below are berries you can pick in the wild? check "Blueberry", "Strawberry", "Raspberry" and "Cloudberry".
   2. Drag and drop: from left to right drag the first image to "Blueberry", the second to "Redcurrant" ans the third to "Cloudberry" (the same as the image attached before)
   3. Which one of the following berries are red? select "Cranberries"
   4. Click on "Finish" button.
   5. Check that your result is 6/6 and a message "Congratulation! You did very well!" appears.
4. Click on the "Retry" button again to start a third attempt with the following answers:
   1. Which of the berries listed below are berries you can pick in the wild? check "Strawberry", "Raspberry" and "Cloudberry".
   2. Drag and drop: from left to right drag the first image to "Blueberry", the second to "Redcurrant" ans the third to "Cloudberry" (the same as the image attached before)
   3. Which one of the following berries are red? select "Cranberries"
   4. Click on "Finish" button.
   5. Check that your result is 5/6 and a message "Congratulation! You did very well!" appears.
5. Login as admin in the course and go to the grade book
   1. Check that the student grade on the activity is 100.

Manual testing 3 (change grading method)

1. With the same scenario as the previous test, login as admin and go to the course where you create the H5P activity
2. Acces the H5P activity and on the cog menú go to "Edit settings"
3. In attempt options change the attempt grading method to "average attempt" and click on "Save and return to course"
4. Go to the gradebook:
   1. Check that the student have a grade of 77.22
5. Edit again the activity settings and change the attempt grading method to "Last attempt" and click on "Save and return to course"
6. Go to the gradebook:
   1. Check that the student have a grade of 83.33
7. Edit again the activity settings and change the attempt grading method to "First attempt" and click on "Save and return to course"
8. Go to the gradebook:
   1. Check that the student have a grade of 33.33
9. Edit again the activity settings and change the attempt grading method to "Don't calculate grade" and click on "Save and return to course"
10. Go to the gradebook:
    1. Check that the student still have a grade of - (empty grade)
11. Edit again the activity settings and change the attempt grading method to "highest attempt" and click on "Save and return to course"
    1. Check that the student still have a grade of 100

 Manual testing 4 (regrade)

1. Continuing in the course of the previous scenario edit the activity settings.
2. Open Grade form:
   1. check that  a message "Some grades have already been awarded, so the grade type cannot be changed. If you wish to change the maximum grade, you must first choose whether or not to rescale existing grades." is present
3. In "Rescale existing grades" set to "Yes"
4. Set "Maximum grade" to 50
5. Submit the form
6. Go to gradebook
   1. Check that the student have a grade of 50
7. Go to the activity settings and now set:
   1. In "Rescale existing grades" set to "No"
   2. Set "Maximum grade" to 80
   3. Submit the form
8. Go to the gradebook
   1. Check that the student still have a grade of 50 (no reagrade has been done)
9. Go to the activity settings and now set:
   1. In "Rescale existing grades" set to "Yes"
   2. Set "Maximum grade" to 100
   3. Submit the form
10. Go to the gradebook
    1. Check that the student still have a grade of 100