Add Jenkins script

This commit adds a script for Jenkinsising the deployment of off-site backup
boxes and associated network (NAT and firewall) rules.
Net: Add `nat.rb`

The `nat.rb` file is a ruleset used to configure NAT rules on the vShield Edge
firewall. This commit adds this file.
Box: Add YAML file for use when launching boxes

The YAML file in this commit is used when launching new GOV.UK off-site backup
machines using `vcloud-launch`.
Add a README for configuring networking

A README for configuring networking. Very useful if you're new to the repository
and want to know how things work.
Amend BACKUP_SERVER_IPS values

There will only, currently, be one off-site backup server on Carrenza. Thus, the
IPs have been changed and the variable name has been changed from `...IPS` to
`...IP`.

It has been left variabalised in order to allow for additional IPs to be added
with limited overhead in future.
Amend firewall rules

This commit:

- fixes the GOVUK_PROD_IP variable:
-- adds a trailing closing bracket
-- adds the P1 production SNAT IP

- removes excess or unwanted firewall rules
- changes comments and variables to reference `backup` rather than `mirror`
Make network config use  vcloud-edgegateway tools

Rather than continue to use `vcloud-net-spinner`, we should be looking to use
the
[`alphagov/vcloud-edgegateway`](https://github.com/alphagov/vcloud-edgegateway)
tool.

This means that we can specify our firewall configuration in one YAML file. This
commit adds that YAML file. It worked fine during testing.
Add vcloud provisioning tools to Gemfile
YAML files
Add bootstrap to `common` directory
Add Org vDC network configuration
Amend box YAML file
Amend org vDC network YAML
edge.yaml: change network, add outbound rule
Add script to create a Fogfile
Add bootstrap