FixedSizeAggregateInGallery

Changed AggregateInGallery to never process more than 1000 records at a time. Currently, 1000 is hard-coded

NOTE: On average, 1000 records take 5 seconds to execute. 10000 could not be completed in the default 30 seconds timeout, so, sticking with 1000

TODO: Make offset a parameter of the job instead of hard-coding it