declared NavigationElementPtr, NavigationTablePtr for consystency
Fixed a bug in SpineItem property parsing.
Fixed some issues with IRI class.
Merge branch 'feature/refcounted' into feature/errors

* feature/refcounted:
  Fixed some issues with IRI class.
  Fixed a bug in SpineItem property parsing.
  declared NavigationElementPtr, NavigationTablePtr for consystency

Conflicts:
	Platform/Apple/ePub3.xcodeproj/project.pbxproj