added referer based return url detection and fixed a couple of minor issues with signin page
reverting change to default return url
Improve email field handling

Tweaked the email validation and added additional properties to email
field display to improve the experience on mobile devices.

Both email and password mappings have been abstracted sine they will
appear in multiple places.
Merge pull request #1464 from guardian/right-hand-story-package

Defend against related content story packages
Merge pull request #1463 from guardian/improve-email-form-fields

Improve email field handling
Merge pull request #1456 from guardian/frj-sigin-fixes

added referer based return url detection and fixed a couple of minor iss...
Merge branch 'master' of github.com:guardian/frontend into external-linked-content-cards