Emergency contacts: refine secondary contacts

* Make the secondary contacts a list
* Push the contact 'role' into the config file
Correct phone number spacing in contact details

This brings the numbers in line with the [GOV.UK style guide](https://www.gov.uk/design-principles/style-guide/style-points).
Fix capitalisation in headings
Emergency contacts: move 'current_at' date into YAML

The 'current at' date needs to be changed along with phone numbers.
Merge pull request #202 from alphagov/emergency-contact-details-refinements

Emergency contact details refinements