Adding the created date as the start date for the google analytics query...

... and adding an earliest cut off for older systems who were not collecting google analytics in the past.

Why the earliest analytics date:
If you were not sending download statistics (that were not included before sufia 4.0) to the system you may want to not say the statistics are valid since when the files were deposited.  Instead you may want to say for older files that the statistics are valid since the time you started keeping track.
Not sure.  I was copying the syntax that was there before.  Since those lines directly affect the file_usage it makes sense that they are there to me, but they can be moved out to...