Research in adapting GRUB to Raspberry PI3 board.

Main concern is to check whether it is feasible to run GRUB on Raspian OS.

If so, then following goals are to achived:

1. Build GRUB for Linux to obtain GRUB tools such as grub-mkimage.
2. Build GRUB for ARM architecture to obtain modules for Cortex-A53.
3. Create GRUB early configuration file to provide kernel and device tree paths.
4. Build grub.efi file.