Simplified APIs

The biggest changes to the APIs are:

1. Tensors are simple script types. So no need to explicitly delete them. The library automatically allocates and deallocates the native Tensor handles used within TensorFlow. Additionally, script arrays can be passed in directly into run().

2. Instead of starting with a Session object, the starting point for the API is now the Graph object (consistency with future Model starting point). Graph has a createSession method.

3. Additionally op references do not need to be explicitly loaded/specified when loading a Graph. Instead the ops just need to be referred to when calling session.run and they are automatically loaded and cached.