Auto-initialize Woodwork

As a user, I think it would be helpful to auto-initialize Woodwork when using the accessor. DataFrames contain enough information to create an initial schema based on the data types. There are several methods to update the schema after initializing.

Additionally, I think this behavior is similar to pandas behavior which does not require data type information to initialize a DataFrame -- you can modify the data types afterward. One possible drawback is losing the option to provide typing information before initializing, but it might be more of a pain point to make this initialization a requirement for the user.

As a developer, I think it would help simplify the code since it wouldn't require adding an initialization check to most (if not all?) of the methods in the Woodwork accessor. There may be some points I've overlooked here, but I think this is something worth considering.