The file python/ray/worker.py is a bit of a mess. We should restructure it in some of the following ways.

1. There should be a Worker class which has a local scheduler client, object store client, and Redis client. It should be possible to instantiate multiple Worker objects. More of the functions in worker.py should be part of the Worker class.
2. There should be a separate Python file that implements the Ray API (and which creates a global Worker object to use as the default worker). The Ray API calls would essentially be forwarded to method calls on the global worker object.
3. The remote decorator should be implemented in a separate file.