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
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
Refactor uk-benefits-abroad to use #next_node_if
Allow overriding of entire label for VariableMatches predicate
Better labels on transitions
Include first line of body on outcome nodes

if there's no title defined for the outcome
Improve graphviz output

- colour nodes
- labels for edges
Make intention of label generation clearer

if there are multiple matches wrap the list of them in braces to make it look more like a
mathematical set.
Use instance variables/accessors consistently