Install heat-cfntools as part of the cloudinit process

Currently we support several mime types for cloudinit. Add a new mime type called x-agenttools which allows cloudinit to save cfntools files to /opt/aws. Then the files that constitute the cfntools are sent at instance start time in the user data. The files that are sent via this user data and their locations are stored in a file in the filesystem in /etc. A config option is added that defaults to disabled to allow/disallow this mode of operation.

This solves the condition of faulty network at pip install time or pip mirrors being down. With this mode of operation, only a distro gold image (with cloudinit installed) is needed in order to initialize an instance.