Implement from_dict in Embedding class

[jaARke]

The Embedding class currently provides a to_dict function for converting class data into a dictionary. It would be easy enough to add a function for the opposite conversion, and such a function might make it easier for users to create custom Embeddings, so long as they were made aware of the supported dictionary structure.

The from_dict function would be a static function that initializes an Embedding object from a dictionary parameter. This would require mapping dictionary fields to class attributes in the same way they are mapped in the to_dict function.