FixedSizeAggregateInGallery. Changed AggregateInGallery to never process
more than 1000 records at a time

NOTE: On average, 1000 records take 5 seconds to execute. 10000 could not be
completed in the default 30 seconds timeout

TODO: Make offset a parameter of the job
Incorporated comments
Merge pull request #16 from NuGet/daravind/FixedSizeAggregateInGallery

FixedSizeAggregateInGallery