Make ytccf.sh's thumbnails display capable of various backends

[frediz]

• none : some may want no thumbnail display or just can't, so --no-thumbnails comes into play.
• ueberzug : by default and can be used in many terminals.
• kitty's icat : autodetected with TERM variable : kitty has its own display helper which handles tabs properly.
• other mean may be implemented.

[woefe]

Thanks!