relocate flexi, fixes #4101

RELEASE-NOTES.md

app/controllers/admin/courses.php

app/controllers/calendar/schedule.php

app/controllers/file.php

app/controllers/resources/booking.php

app/controllers/room_management/planning.php

app/controllers/shared/download.php

app/controllers/start.php

app/views/file/file_details.php

app/views/file/folder_details.php

app/views/file/new_edit_folder_form.php

app/views/files/_fileref_tr.php

app/views/files/_folder_tr.php

app/views/files/flat.php

app/views/files/index.php

app/views/start/index.php

...rules/conditionaladmission/ConditionalAdmission.class.php

...les/coursememberadmission/CourseMemberAdmission.class.php

...dmissionrules/limitedadmission/LimitedAdmission.class.php

lib/admissionrules/lockedadmission/LockedAdmission.class.php