Adds root_object getter to engine.
Adds root_object getter to engine.

Jyaasa/rabl,infertux/rabl,Jyaasa/rabl,bholzer/rabl,nesquena/rabl,zoyi/rabl,bholzer/rabl,Jyaasa/rabl,infertux/rabl,infertux/rabl,nesquena/rabl,zoyi/rabl,sideci-sample/sideci-sample-rabl,sideci-sample/sideci-sample-rabl,bholzer/rabl,nesquena/rabl,zoyi/rabl