OO-2791: show an error message if a question of the pool is not readable during the import in a test

OO-2772: replace the all answers score per a default value which make more sense than -1.0, fix equal method of the gap wrapper

OO-2757: check keys and type in test course element to prevent error due to switch from test with QTI 2.1 and 1.2

OO-2748: check assessment entry visiblity for show results, init the whole thing after suspend and cancel too

OO-2740: remove the email of the person leaving the group from the email to the person gaining access to it (patch S. Clemenz)