reorganized source code for all basic object definition/augmentation
[#291] Disable ObjectEntity falling flag when there is no gravity.

- Thanks @Deathspike for #478
[#482] Fix an exception in ObjectEntity.checkCollision()

- See: https://groups.google.com/d/msg/melonjs/w6UawD-I3Dw/SNY1cNy8wcEJ
- Reset the me.game.collisionMap reference to an empty collision map.
- The empty collision map is only created once at startup.
Update CHANGELOG
fixed up coords
Merge branch '1.1.0-dev' into debug-panel-scaling