Merge remote branch 'upstream/develop' into develop-next

include/class.attachment.php

include/class.i18n.php

include/class.mailfetch.php

include/class.mailparse.php

include/class.osticket.php

include/class.thread.php

js/redactor-osticket.js

kb/file.php

scp/file.php

scp/js/scp.js

setup/test/tests/test.validation.php