Add direct datafile upload support (directupload.py) to pyDataverse

[cmbz]

Background
Support for direct upload of datafiles using Python is available via the following standalone script related to the Harvard Dataverse Repository: dataverse.harvard.edu/util/python/direct-upload/directupload.py

This script enables users to upload many datafiles and their associated metadata all at once before requesting reindexing, rather than calling the API for each file resulting in a system performance hit due to frequent reindexing.

Request & Rationale
Incorporating this functionality into pyDataverse would benefit Dataverse API users and pyDataverse users at all installations who need to upload large numbers of datafiles.

[pdurbin]

@cmbz for now @JR-1991 has created a separate uploader. Please see:

• add python-dvuploader to client libraries page IQSS/dataverse#9946
• https://github.com/gdcc/python-dvuploader