Script to copy and sanitise the Whitehall database

This adds a shell script that sanitises the database of potentially sensitive information, e.g email addresses, access limited drafts etc.

It's mostly written in pure SQL for speed, which means it may get out of sync with the production schema.

Put up early as a pull request for feedback, especially @samjsharpe and @heathd.

https://www.pivotaltracker.com/story/show/40325147