Document the process of re-spinning an image

Document the process of re-spinning an image

* Document the process of respinning jcloud images in README.txt
* Create /scripts/respin-jcloud-images.sh
* Create /vagrant/lib/respin-functions.sh
* Automate the process of fetching latest base images
* Automate the process of creating new "LF upload" snapshots
* Automate process of creating jcloud image
- Boot fresh VM
- run bootstrap.sh
- run system_reseal.sh
- snapshot re-sealed system
* Unable to automate updating jcloud image regex for staging nodes
* Correct shasum to sha1sum
* Add cloud-initramfs-* to PACKAGES list
* Install cloud-init during system reseal

Change-Id: Ie70d5f1fdee0e9f06810da6f37bfc710e3e06b8e
Signed-off-by: C.J. Collier <cjcollier@linuxfoundation.org>