Choko Multi OS system images

Scripts to make or update custom multi boot system.

Version 1.6.1:

• Fix mounting the CHOKO_DISK/remappings folder in wrong place for Batocera 38 (and probably 37).

Version 1.6:

• Updated upgrade scripts to check if there is enough space in CHA_BOOT partition before starting to copy.
• Some fixes and improvements in updater scripts, like making sure writing the files in CHA is completed before exiting.

Batocera 35 also included, since it a bit lighter than v38 and some might prefer it.