Add aggregator for frequency metadata rows

[lbschanno]

Create the aggregator FrequencyMetadataAggregator. This aggregator will support compaction of the "f", "i", and "ri" columns in the metadata table, collapsing the counts for dates into a single entry for each unique row, data type, and column visbility grouping.

Update MetadataHelper and AllFieldsMetadataHelper such that methods scanning over either the "f", "i", and/or "ri" columns are able to handle entries that either have the original format created upon ingest, or the aggregated format generated from the aggregator.

Required for datawave/issues/716.

[ivakegg]

So I loaded this and set this as an iterator on the datawave.metadata table using datawave-quickstart

ashell
setiter -t datawave.metadata -scan -class datawave.iterators.FrequencyMetadataAggregator -p 13

Then scanned the various column families. It works if I keep the scan down to the i, ri, or f columns although the i and ri values appear to be all zeros:
scan -c f
scan -c i
scan -c f

However if I can a field like EVENT_DATE, then we bomb:
scan -r EVENT_DATE

We need to be able to configure the column families to aggregate. As an example see the Combiners that we currently configure on the datawave.metadata table.

[lbschanno]

@ivakegg understood, I'll add an option for configuring the column families.