Headless merge with develop

You mentioned something about headless breaking.

I'm pretty interested in a headless (or possibly 2d) mode since my system is barely on the edge of running Terasology 3d, and most of the work I'm doing is with NPC characters.

I've merged the latest develop into headless.   I'm still trying to determine what starts the system in headless mode.   It looks like Environment is intended to replace TerasologyEngine?

Anyway, here's my merge work.