Add DatabaseProtabilityService

To help support Oracle and PostgreSQL while avoiding code duplication.
Unfortunately, there are a lot of SQL queries that don't go through
hibernate.
Round p-values in faceted searchʼs heatmap

The Oracle version doesn't need this because the ETL already puts
rounded values on the final table due to NUMBER columns with limited
precision in intermediary tables. We use plain double precision types in
those tables.
Make RWGVisualizationDAO a servic

Also add bare minimum PostgreSQL for showing the heatmap in faceted
search.