Add linux-stable repo as submodule

URI:git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git src/linux-stable
Update linux-stable to v3.17.1
Add the initramfs config file
Add makefile with target for building the linux kernel
Add a git ignore file.

Initially ignores the output directory only
Add microinit as a submodule
Update src/microinit submodule
Add microinit target ot the makefile