Also performed the following -
1) Deprecated the assignment's add_to_log function (part of it's functionality exists in the base class to set the legacy log data).
2) Edited existing events to use the new base class.
3) Renamed event_test.php to events_test.php to match the rest of core.
4) Moved the event tests from locallib_test.php to events_test.php.
5) When setting legacy data use lang_string, rather than get_string, as we may not be using them if legacy log is disabled.
New events have been created for submission plugins. This is
part of the consistancy move by adding the same type of event through
all of the modules.
AMOS BEGIN
MOV [event_submission_updated,mod_assign],[eventsubmissionupdated,mod_assign]
AMOS END
