Use unique names for all resources

[RothAndrew]

If 2 people run terraform apply using the same variables, name conflicts will occur. For example, If 2 people use bastion_name = "my-bastion" in the same aws account, IAM policies such as "my-bastion-s3-readonly" (and a bunch of others) will have name conflicts.

This is likely to happen as we introduce automated testing. I'm surprised it hasn't already just from people reusing the same example tfvars files in the same account.

We could append some UUID to every resource name/id. We do this for certain things already by applying what looks to be a datetime stamp, but we don't currently do that everywhere.

[RothAndrew]

Clarification: We should make the modules take care of adding uniqueness. Currently in #90 the example is defining unique names and passing them to the modules.