move mail template editor from core to standalone templateeditor repo

apps/files_sharing/app/sharing.php

apps/files_sharing/appinfo/app.php

apps/files_sharing/appinfo/routes.php

apps/files_sharing/controller/adminsettingscontroller.php

apps/files_sharing/css/settings-admin.css

apps/files_sharing/http/mailtemplateresponse.php

apps/files_sharing/js/settings-admin.js

apps/files_sharing/lib/mailtemplate.php

apps/files_sharing/settings-admin.php

apps/files_sharing/templates/settings-admin.php