Merge branch 'm_MDL-31552_change_add_to_log_exception_to_add_exception_information' of git://github.com/gerrywastaken/moodle

MDL-31552 Change add_to_log() so that it's exception handling throws a useful message when there is a problem.

MDL-31112 Repository upload - check for completely null files (likely to be folders uploaded by mistake via drag and drop)

Merge branch 'm_MDL-26807_remove_withselectedusers_strings_and_references' of git://github.com/gerrywastaken/moodle

Merge branch 'm_MDL-27285_fixing_grammar_on_wiki_links_page' of git://github.com/gerrywastaken/moodle

Merge branch 'm_MDL-27654_add_space_to_somefieldrequired_string' of git://github.com/gerrywastaken/moodle

Merge branch 'm_MDL-30935_lti_change_instructor_role_to_teacher' of git://github.com/gerrywastaken/moodle