Enable request forgery protection for features

Bulk edit without js has been broken for a few months due to a missing
authenticity_token, and we didn't notice. This change will mean that
features should fail if we do this again.
Remove trailing whitespace from 2 lines.
Include authenticity_token for non-js bulk edit

Since Rails 4.0, remote forms have not included authenticity_token
by default:

    https://github.com/rails/rails/commit/128cfbdf4d316a544a76e5c58dbeac153f3d4e36

The form_tag needs to have `remote: true` to work in the modal, but
also needs the authenticity token to work without JavaScript. This
commit includes the token in the form via the helper's options and
fixes the features which were failing on the missing token. We
don't use remote forms anywhere else in the app.
Merge pull request #416 from alphagov/fix_bulk_edit_without_js

Fix bulk edit without JavaScript
Change select boxes to radio buttons for mapping type selection

- Radio buttons make switching between types when editing a mapping
  easier. It's one click rather than 2/3, and you can see the options
  sooner. This has been a minor usability problem in user research.
- Make the radio button style consistent with the non-JS filter mappings
  radio buttons: all on one line.
Fix indentation of the Type label and radio buttons in forms
Use the existing mapping type as the selected radio button on edit

- Switch to using the Rails form helpers in one case.