renamed Visible to Availability and added help strings
AMOS BEGIN
CPY [availability,core_moodle],[modvisible,core_moodle]
CPY [availability,core_moodle],[modvisiblewithstealth,core_moodle]
CPY [availability,core_moodle],[modvisiblehiddensection,core_moodle]
CPY [show,core_moodle],[modshow,core_moodle]
CPY [hide,core_moodle],[modhide,core_moodle]
AMOS END