Add a "setting up a metadata server" guide

[davidorme]

This should step through the process of getting up and running, rather than day to day validation.

• Build initial resources - gazetteer, location aliases and optionally project database.
• Setup server
  • Decide on local projection for use in distance calculations
  • Get server running using description in safedata_server
  • Update resources
  • Run a test case using the sandbox
  • This then needs a way to remove the details for a published dataset - which is probably something we need anyway.