Add base year to summary

[vgeorge]

The PR #67 enabled base year data ingesting, but there are other parts to be implemented to enable this feature:

• Validate base year fields
  • check if present (see names at Add baseline to summary and tooltips explorer#188)
  • check if valid number
• Include base year data in /scenarios/{id} summary
• Include base year data in /scenarios/{sid}/features/{fid} summary