To set a base for upcoming docs changes, the docs directory structure
has been streamlined to follow a simplified version of Django's docs.
The old _draft folder has been removed. Both files from there and the
current docs that don't fit nicely into the new structure are in _old/
for the moment.
Clean up documentation typos (e.g., use 'e.g.' instead of 'eg'; misspellings; GitHub vs Github; consistent use of Oscar vs oscar or django-oscar when referring to the product)