108: Finalised Bastion Host Addition

A Bastion Host which lies in the PublicSubnet. It controls who can and who cannot SSH into the app EC2 servers. This is done via public keys that are put into "pop-staging-bastion-keypairs" bucket in ap-southeast-2 

Upon creation of the stack, any key pairs that exist in the bucket are moved into the bastion host. 

At the moment, only SSH is let into the bastion host and nothing else goes out through it.

:pear: @3000