Call StartGame() from MainGame.Start Coroutine.
Call StartGame() from MainGame.Start Coroutine.

This is a first step towards .NET Framework 4.0 compatibility.

Without this change, StartGame can be called from a non-Main Thread when running the game,
which does not allow calling UnityEngine.Object methods such as FindObjectsOfType.

Change-Id: I4fc00a53ce239019dbdbcefc9d6610c50d79edfb

google/mechahamster,google/mechahamster