VolkovCommander-like chain menu

[akorop]

(See ticket #3925)
Proposed patch add menu chaining, as in Volcov Commander. Additional menu files must be placed in the user config directory (~/.config/mc). Reference to the next menu is the single line beginning with ">". For example:
~/.config/mc/menu

.....
+=  t r & f *.avi | f *.ts | f *.mp4 | f *.mkv | f *.wmv | f *.flv| f *.3gp | f *.webm | f *.mov
v video menu
   > video.menu
....

~/.config/mc/video.menu

back
   > menu
edit
   screen -d -m  avidemux3_qt5 %f
info
   %view mediainfo %f
mpv
   screen -d -m mpv -fs %f

To do: help