Make the author of a document accessible through the API

[michaelkroll]

If you are dealing with granting access to documents to other users it might be good to be able to read the author attribute on a document to show to the user who owns it.

[neil-oliver]

I needed this so i modified the SDK by taking the author line from the top of the BAAfile.h and BAAfile.m and putting them into the BAAObject files. It was a simple copy and paste. Not sure if it was the correct way of doing it or a reason that it wasn't implemented but it seemed to work for me!