Create a new Subject structure to describe a move event
| source_uri | The URI or URL of the subject | 
| source_origin | The URI or URL of the subject | 
| destination_uri | The URI or URL of the subject | 
| destination_origin | The URI or URL of the subject | 
| interpretation | The interpretation type of the subject. | 
| manifestation | The manifestation type of the subject. | 
| mimetype | The mimetype of the subject. Eg. <emphasis>text/plain</emphasis> | 
| text | A small textual representation of the subject suitable for display | 
| storage | String identifier for the storage medium the subject is on. | 
| A newly create Subject instance. The returned subject will have a floating reference which will be consumed if you pass the event to any of the methods provided by this library (like adding it to an event). |