EZP-20172: Refactored Output\Visitor to use Response natively
EZP-20172: Added CachedValue REST objects + visitors
EZP-20172: Made REST http cache vary on Accept
EZP-20172: Cached more resources

- /content/locations/{locationPath}
- /content/locations/{locationpath}/children
- /content/{contentId}/locations
- /content/{contentId}/relations
- /content/{contentId}/relations/{relationId}
- /content/{contentId}/versions
- /content/{contentId}/versions/{versionNumber}