SW: add binwalk to GRML_FULL

Quoting Marc Haber from the bugreport:

| binwalk is helpful when unpacking one of those nifty new initrd
| images with microcode prepended. binwalk tells you how many bytes
| to skip at the beginning of initrd.img to find the beginning of
| the actual initrd.
|
| Usage example see
| http://unix.stackexchange.com/questions/163346/why-is-it-that-my-initrd-only-has-one-directory-namely-kernel

Closes #21 @ GH