Defined the first version of the GameContainer interface.

GameContainer inherits from GameObject

Right now the implementation is looking like it's going to duplicate a lot of the
information in CEsmContainer.  It might be better to just wrap a CEsmContainer object.

Also, containers and there contents are shared across cells so when adding for the first time, 
need to create a new custom container.  Basically need to make sure not modifying containers
elsewhere in the world, i.e. create a new container from some existing base container.

TODO:

  * comments
  * find out where to get size information
  * implement GameContainer class
  * need to load the database of game objects