The only different between each setting dependency type is the evaluation of the condition,
and the mform js validation arguments - so that should be the only thing that is extended
by each subclass.
The function is_locked was changed to determine only, if the
dependency_setting want's the dependent setting to be locked.
In the previous version, is_locked did not only check, if the
dependency_setting want's the setting to be locked, but also if the
setting was already locked. A recursive call to the status of the
dependent setting leaded to problems, when unlocking locked settings.
Also the PHPDOC of the is_locked was adjusted to coincide with the current
usage in backup_ui_settings->is_changeable() and
base_setting->set_status(). In both functions all dependency_settings of
a setting are iterated to check if this setting should be or is LOCKED_BY_HIERARCHY.
The actual state of the setting was therefore either checked beforehand
or is not interesting, since the question is, if it shall be changed.
This commits cleans some code (settings and dependencies)
and one file included previous by error.
Also it disables all the IMS-CC export feature by default, being
possible to enable it under demand by setting (@ config.php):
$CFG->enablebackupconverters = true;
