Organize / Improve object ownership

[colbybhearn]

It's useful to be able to know a client and get the objects it owns.
It's useful to be able to know an object and get the client that owns it.
It's useful to be able to know if an object is owned by anyone.
It's useful to know this information on both the client and server

Perhaps the AssetManager should be responsible for this.
Perhaps Gobjects should have an integer property OwnerClientId.

[Quintinon]

ClientObjectIds in BaseGame.cs provides some of this functionality already for both client/server. This is how the client knows which name to display above an object.

[colbybhearn]

Moved ClientObjectIds into AssetManager. The objectsOwnded and ClientControlledObjects in BaseGame still need to be moved into AssetManager. More work was put into making asset identification (and enumeration) easy and clean (See RoboGame.Assets)