This commit moves the Amazon builders of Packer away from the Hashicorp
fork of the goamz library to the official AWS SDK for Go, in order that
third party plugins may depend on the more complete official library
more easily.
This reverts commit b2fc77870b825403ea068ba63f66ac28c76b3e88, reversing
changes made to 4789d3acc8937757ee7a430199bbc39671ba93c7.
This is already possible by setting groups.
/cc @jmassara - I pulled out the AMI stuff into a common config
struct and also added in the new template stuff (that didn't exist
when you made the pull, so not your fault! :))
