Blender Git Loki

BGE : addObject in python without reference object.

Making the reference argument optional for the addObject function.
```
scene.addObject("Cube")
```

This allows to keep the rotation, scale and position of the original object.
To avoid layer problems with lights if the reference arguments is None, the new object have the same layer than the active layers in scene.

Reviewers: lordloki, moguri, hg1, sybren

Reviewed By: hg1, sybren

Subscribers: agoose77

Projects: #game_engine

Differential Revision: https://developer.blender.org/D1222