Add previews for emails

These can be viewed in development mode at
http://localhost:3000/rails/mailers

The last claim is used to generate the preview, so there must be at
least one claim in the development database for previews to work.
Containers for the HTML

- Copy is being done ATM
WIP

- Converted the email to slim
- Made a couple of partials. good idea?

__Need help with..__
- conditional logic in the partials
- getting data from the model
Moved shared files

..and split the header in to two rather than use conditional logic
fixed indentation
Merge new template with access details email

TODO: the complete application link in the email doesn't go anywhere
useful. It didn't go anywhere useful before, either.
Use real link back to app in access details email
Use translations for access details email
Update copy on access details email
Updated copy, new partial

- updated image urls
- fixed indentations
Button partial

- fee remission
fixed layout bug after new partial
Make claim number legible again
Style the Complete Application button in email
Copy updates

- small refactor to move submission details into the table
- updated footer
- added another logo
Expose unpaid? and fee_to_pay? on Claim

This will allow us to put some reasonably sensible logic in the email
template to determine when a payment has failed. The obvious route of
putting a "payment_failed?" method on Claim doesn't quite make sense
because that's only a correct inference in certain states.
Delegate directly to payment

It makes more sense to check unpaid via the absence of a payment than to
negate its presence.
Email subject no longer contains claim reference

Fixes tests that expected this.
New style (and logic) for confirmation email
Remove unused emails

These are different views of the confirmation email, which now
incorporates these changes.