Add general purpose support for predicate union (or)

aliased to `|`.
Update overseas-passports to use next_node_if

also refactored to use predicates which generate helpful labels
Convert maternity-paternity-calculator.rb to next_node_if
Convert register-a-birth to #next_node_if
Refactor register-a-death to use next_node_if
Content update
Content update
Manually track pushState pageviews with GA

The version of GA we're using doesn't do this automatically, so ensure we capture all the steps in Smart Answers
Merge pull request #925 from alphagov/fix-push-state-tracking

Manually track pushState pageviews with GA
Update register a birth and death V2 flows

- Updated next node in flows
- Additional methods in registrations data query
Merge pull request #923 from alphagov/stat_sick_calc_update

Smartanswers - statutory sick pay - content update
Merge pull request #924 from alphagov/intestacy_update

Smartanswers: intestacy - Content update
Merge pull request #904 from alphagov/static-next-node-step2

Convert another batch of smart answers to use new next_node syntax
Whitespace
naming
hash syntax
Case indentation
remove comment spacing
case indentation, tab removal
Flow update
Same outcome should show for countries in which is possible to marry a person of the same sex whether the user lives in the UK or not