Remove subtitle field

It's only used in tests and sample content
Remove test for Bridge of Death subtitle
Merge pull request #1050 from alphagov/remove-subtitle-feature

Remove subtitle field
Added content about dual nationals to start page
Merge pull request #1051 from lutgendorff/patch-5

Added content about dual nationals to start page
Updating Student Finder Forms smart-answer

Change v2 files to v1
Merge pull request #1055 from alphagov/switch_student_forms_to_published

Updating Student Finder Forms smart-answer
Smartdown in smart answers application
Use Ruby enumerables for body and devolved_body
Documentation for both styles of smart answers
Merge branch 'smartdown' of github.com:alphagov/smart-answers into smartdown

* 'smartdown' of github.com:alphagov/smart-answers:
  Documentation for both styles of smart answers
  Use Ruby enumerables for body and devolved_body
  Smartdown in smart answers application