subtitle edit: add text input to edit subtitle name

will make it easier to add new subtitles
(currenlty possible only using URL param &subtitle_id+<name>&action=edit )

Note: have to lowercase subtitle_id
subtitle overview: adding button to create subtitle

will make it easier to add new subtitles
(currenlty possible only using URL param &subtitle_id+<name>&action=edit )

Note: have to lowercase subtitle_id