add Git submodule Makefiles

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
Initialize root Makefile for the repo

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
Initialize VERSION file

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>