Re-compile Guessit Result

The GuessitResult should be re-compiled and better documented. It should also be moved into its own package, as it is at the core of all interfaces and should be available for documentation (schema/ result/?). The type can be aliased into clients to simplify imports.

Additionally, the known values of fields should be collected and added as untyped (? to indicate non-exhaustiveness) string constants.

Sources of properties and values:

• https://github.com/guessit-io/guessit/blob/develop/docs/properties.rst
• https://github.com/guessit-io/guessit/blob/develop/docs/migration.rst
• https://github.com/guessit-io/guessit/blob/develop/docs/migration2to3.rst