Implement Document Versioning

[aeshthetic]

Authors should have the ability to re-upload their works such that viewers can see the history of the document as it has been re-uploaded over time.

[aeshthetic]

Documents are now versioned, versions are stored in the database, and history can be viewed from the profile page or the browse page. It would be nice to have a sidebar displaying all versions of a text when the text is open, though.