Create a new humanitarian_statistics table

Create a new table that is run outside of the IATI refresh/reload process that is capable of reducing the raw_iati_activities, raw_iati_transactions, and iati_publisher_frequency table into statistics about humanitarian publishers. Until the iati_publisher_frequency table can be populated with enough timestamps to make meaningful use of it, the frequency statistics may need to be replicated from another source of data.

No files, tests, or entry points are named in the issue. Start by locating the raw_iati_activities, raw_iati_transactions, and iati_publisher_frequency definitions and the IATI refresh/reload process; done should mean a separate humanitarian_statistics table produces meaningful publisher statistics without running in that process.

Written by the indexing model from the issue text.