Record filepicker URL before convert_raw_document so we can associate anonymous users with notes better

[btbonval]

RawDocument, which is passed into convert_raw_document(), has fp_file attribute which is the filepicker URL. It is even used by get_file() here: https://github.com/FinalsClub/karmaworld/blob/master/karmaworld/apps/notes/gdrive.py#L183 https://github.com/FinalsClub/karmaworld/blob/master/karmaworld/apps/document_upload/models.py#L25 https://github.com/FinalsClub/karmaworld/blob/master/karmaworld/apps/notes/models.py#L127 https://github.com/FinalsClub/karmaworld/blob/master/karmaworld/apps/notes/models.py#L88-L92

I included a logical traceback from convert_raw_document() back to the Document abstract class to show this is the case.

This ticket seems more about associating anonymous users with their uploaded links, which makes sense. Do we want to attribute RawDocuments to anyone? They do sort of float around forever, storing duplicate information, without any further purpose after they've been converted. I have a ticket somewhere suggesting they be deleted once converted.

[charlesconnell]

Working on beta now