feat(build_image): install the au-key

Install the developer au key on production images. This will need to
change when we have the production key.
fix(cros_make_image_bootable): no more bootkernel

the bootkernel is going away and we will just have a single kernel for
all of the things. This is because of the kxec on xen problem.
fix(cros_make_image_bootable): need to mkdir first

The au directory doesn't exist. Make the directory first.
feat(build_image): official lsb-release on prod images

The /etc/lsb-release should have official values on the prod image. That
way someone can ping the official api.core-os.net with this image.
feat(build_library): reintroduce A/B menu.lst

reintroduce unique A/B menu.lsts to work around the kexec problems that
we have. Essentially instead of always using boot_kernel on pvgrub
systems use the A/B kernels installed at update time to the boot
partition.
chore(*): remove obsolete stuff

- mod_for_factory says it is obsolete
- coreos doesn't sign ssds
- download_latest is just wrong for us
chore(*): use coreos_ everywhere
chore(build_library/create_legacy_bootloader): remove old stuff

We don't need all of these args. Remove them.
feat(create_legacy_bootloader): add hvc0 on Xen

add console=hvc0 for systems that use pygrub/pvgrub by adding it to the
menu.lst files.
fix(make.conf.user): Fix references to old make.conf.user path.

We've moved all of the chroot configs from /etc to /etc/portage but
setup_board was still symlinking to /etc. Fix the path so no one gets
mixed up by the two copies of the same file. Remove unused script that
also used to write to old location.
fix(setup_board): Install baselayout with USE=build

We need to install baselayout with the build use flag as the very first
package in the new board sysroot to ensure the system's directory
structure is created correctly. This should resolve surprise failures
with the bootengine ebuild.
fix(install_toolchain): Prevent tar from replacing lib symlinks

The cross toolchain doesn't have lib symlinks but this works because it
also doesn't install things to lib. However when this script manually
extracts the toolchain packages to BOARD_ROOT tar includes those empty
directories, replacing the symlinks that were previously there.

Longer term this really needs to go away, whatever build time is saved
by re-using the cross toolchain packages in BOARD_ROOT is not worth this
insane level of complexity it causes...
fix(enter_chroot): Limit sharing system mount sharing

The existing code seems to assume that the mounts inherited from the
system are private, the Linux default. However on our systems that
clearly isn't the case, all system mounts are set as shared. Considering
all of us have been have been seeing mounts leak out of the SDK despite
cros_sdk creating a new filesystem namespace via unshare I'm guessing
this is a systemd thing.

Instead force all system mounts to 'slave' mode in the SDK namespace so
global changes are still visible but no SDK mounts can leak out.
add rackspace
chore(*): use COREOS lsb-release variables

use the COREOS_ variables in /etc/lsb-release
feat(image_to_vm): Refactor to make adding/changing vm formats easier.

The old script was heading towards spaghetti code realm. This breaks up
all the image variations such as hybrid MBR, OEM packages, etc into
configuration options and small functions that actually do the work.

All this is in the new vm_image_util.sh library but the command line
parsing and overall procedure remains in image_to_vm.sh

As part of this we gain support for putting some qemu options in a
config file as well as Xen virtual machines using pygrub and pvgrub.

Lots of generally unused options have been removed to simplify things
and keep output file names consistent.
fix(vm_image_util): Remove tab characters.
fix(vm_image_util): Remove space before # comment in qemu config.

Last minute bug slipped in because of a line I commented out since the
current coreos kernel doesn't support virtio block devices (that change
coming soon). Qemu doesn't tolerate any spaces before # in comments.
add ebs script
add scripts