VirtualBox script changed to convert image untouched

With config drive there is no need to crack image to insert SSH keys. Then VirtualBox script was changed to just download CoreOS image and convert it to VDI format.
Script to create basic config-drive

New script that creates a basic config-drive, ideal to testing purpose.
feat(core_promote): Mark old GCE images as deprecated.
feat(OpenStack): Add new scripts to support OpenStack OEM handling

Included are scripts to monitor the CoreOS remote etag, as well as
load a new image into a OpenStack Glance image store.
fix(disk_util): Install syslinux with extlinux

Attempting to work around an apparent race in mtools, the command
'extlinux' these days is just the install tool for mounted partitions
while 'syslinux' is for unmounted devices.
Merge pull request #280 from marineam/extlinux

fix(disk_util): Install syslinux with extlinux
configure_bootloaders: only add a single serial console boot arg

Only one console of each type (virtual, serial, etc.) is supported
in the boot args. Only add ttyS0 if no other serial consoles have
been provided.
Merge pull request #281 from crawford/bootargs

configure_bootloaders: only add a single serial console boot arg
Merge pull request #278 from marineam/deprecate

feat(core_promote): Mark old GCE images as deprecated.
update_metadata: continue if there are no updates to commit.
updates: Add script for enabling the official update signing key.

This script should be called before running build_image when generating
official production images. Images built with official key will not
accept updates signed with the default development signing key.
build_image: check that set_official wasn't forgotten in official builds
Merge pull request #282 from marineam/metadata

update_metadata: continue if there are no updates to commit.
updates: extract usr partition when building images

The current generate_update function is now less useful, the important
part that we need is just the partition image now. Also by defaulting to
extracting the partition the old cors_generate_update which is still in
use by devserver can be removed entirely, devserver will just expect the
extracted partition image instead.
updates: use HTTPS for fetching update payloads
Merge pull request #283 from marineam/version2

updates: Add script for enabling the official update signing key.
core_sign_update: initial commit

Takes a filesystem image and generates a update.gz that is signed by N
provided private keys and verified against the N public keys. This is so
we can do keyrotations.
Merge pull request #284 from philips/multikey

core_sign_update: initial commit
build_image: refresh scripts bundled into the update zip.
build_image: generate update tools zip by default

Missed this in 7231b95a, the update zip should still be built when the
usr partition is extracted for generating updates but build_image itself
is not generating and signing the update.