[FEATURE] Iterator, ObjectStorage, DomainObject support in Format / Json / Encode ViewHelper

This adds full-blown Iterator, ObjectStorage and DomainObject support when encoding to JSON. Recursion protection is engaged and has the option to define exactly what should be inserted instead of objects which cause recursion. This allows special "fake" objects to be created which for example can highlight the currently viewed parent object in a list of related objects which happen to contain the parent object itself (example: playlists with highlight of current track/video/image).

@dreipunktnull would you be willing to check this out to see if I made any stupid mistakes? :)