v2.28.5: Risk answers follow Meridian's risk model; numeric breakdowns fixed

• Risk answers follow Meridian's own risk model. Rankings order by Risk_Score, tiers come from
  Risk_Level, and a record with no risk factor is reported as "no risk factors identified", never
  as low risk.
• Breakdowns by a number field now count correctly. summary --by on a numeric field or
  SmartLabel used to report every group as 0.
• The reference docs use illustrative figures throughout.