Analytics API loader saves data availability by both tracking id and merchant id

To handle stack and reseller level tracking ids, we must keep track of data availability at the tracking id level. Additionally, one row should be included in the availability table for each merchant id found for each tracking id. We also should support receiving data from more than one tracking id per merchant.

This table should also contain the isGolden flag from reports so that we can know which tracking id and day combinations downloads should never be attempted for again.