Clean up the scripts directory
Add RHEL specific script for vbox guest additions

When installing the guest additions on CentOS, we need to install the
"Development Tools" package. This is obviously specific to CentOS, which
is why the script has been renamed to an RHEL distribution.
Use RHEL script to install guest additions
Provision postgres
Remove postgres user from sudoers
Copy keys directory to machine

This is done so that the postgres public key can be authorized.
Ignore .iso and .box files
Add script to authorize postgres public key

Obviously, real production keys should never be shared like this.