To allow reusing the platform independent part of init.rc without having
to copy it for each platform. Also add a bunch of comments explaining
the purpose of each section.

Without this when rebuilding it will try to remove symlinks created by
the cookbook that have been replaced with actual directories in the
previous build.

Signed-off-by: Anhad Singh <andypython@protonmail.com>

Signed-off-by: Anhad Singh <andypython@protonmail.com>