Add question_updated/question_removed_from_quiz events to track_e_default

[ywarnier]

In api.lib.php +280, we have LOG_QUESTION_CREATED and LOG_QUESTION_UPDATED as constants, that are used to log things in track_e_default.

However, we don't have a LOG_QUESTION_DELETED nor a LOG_QUESTION_REMOVED_FROM_QUIZ to register those changes in a searchable way (only track_e_default data is shown in audit lists).

The events are registered in question.class.php::delete(), though, so "plugging" that there should be easy.

This appeared in the light of internal customer issue BT#16465

[ywarnier]

With the addition of these variables, the audit now shows some info about these actions: