This does not have the careful result rechecking that chef has, when it
installs each package in the list one at a time. So to help with failures
caused by a package failing to download, first try downloading all the
package, then run the install. The install pass will try to download any
missing packages.
Really, this should use ansible or perhaps chef again since those include
lots of tricks around this stuff.
This makes it so there is only a single `apt-get install` command run,
instead of one command per-package like with the chef script. It also adds
`apt-get upgrade` to make sure that the base box is fully up-to-date.
