v3.0 : Generate "menuentries" in a separate file

GRUB shouldn't break anymore (#46)

• Update 41_snapshots-btrfs

Enhanced error handling :
- new function available: print_error
- if btrfs-progs is not present, print a error and exit

New options in etc/default/grub
- disable this script

Enhanced menuentries:
- menuentries is now store in new grub configfile (/boot/grub/grub.cfg)
- use new functions for make a menuentry: make_menu_entries and entry
- harmonize menuentry with matching version kernel&initramfs # initramfs-linux-fallback is include and not boot with intel-ucode if exist , same as original patch in GRUB for Arch Linux
- make a menuentry in Grub menu (grub.cfg) to load our configfile

Enhanced /boot detection:
- create two separate function for make menuentries, if /boot is on a separate partition, use function boot_separate, else, boot_bounded
- if no kernel found, print a message and exit
- if no initramfs found, print a message and exit

Delete function: boot_dir
No longer uses gettext_printf function of grub-mkconfig_lib

New function to detect kernel:
- add all original standard kernel
- verifying if kernel exist before to continue

New functionto detect initramfs:
- add all original standard initramfs
- verifying if initramfs exist before to continue

New function to detect microcode

New counter:
- add a counter to show a warning if the total menuentries made exceeds 250 entries

Purge some obsolete code

Size tabulation is now 4