OO-2636: export percent in real excel percent, wording, teachers cannot open lecture blocks before the start date

OO-2866: check if the test is ended before resuming and some small chaanges to handle the case without NPE

OO-2636: implement adaptation of absence if the number of lectures changed, make dedicated close / cancel method in service, implement disable state for auto completer, replace the last step of the wizard, check effective number of lectures agains cancelled status...