[FEATURE] change folder sub-division in var

WARNING: breaking change.

Folders in Jirafeau are originally split with 1 char.
e.g: a/3/b/c/6/f/1...

This is now set to 4 chars for better lisibility.
Older Jirafeau installation can put back to 1 char by editing this file.
This could eventually be a configuration item.

Signed-off-by: Jerome Jutteau <jerome@jutteau.fr>