* Dynamically retrieve aws_bastion_ami latest reference by querying AWS rather than hard coded
* Dynamically retrieve the list of availability_zones instead of needing to have them hard coded
* Limit availability zones to first 2, using slice extrapolation function
* Replace the need for hardcoded variable "aws_cluster_ami" by the data provided by Terraform
* Move ami choosing to vars, so people don't need to edit create infrastructure if they want another vendor image (as suggested by @atoms)
* Make name of the data block agnostic of distribution, given there are more than one distribution supported
* Add documentation about other distros being supported and what to change in which location to make these changes
