Draft: Improve source

Closes #163

TODO

• Create Source model
• Migration
  • Create IGC and Virgo sources in migration
  • Link Gene to Source in migration
• Add Serializer and update Serializer for Gene
• Add custom command to create sources
• Add API endpoint to list sources
  • Basic endpoint
  • Extended information from doi.org
  • Requests cache for doi.org -> API to unstable
• Update filters on API
  • Update backend filters
  • Query source list from frontend to list available source to filter on
• Update scripts to generate light DB
  • Update Factory for Gene
  • Create Dummy sources
• Update way to compute statistics
• Update Frontend
  • Use correct source in list
  • Add Source component
  • Add source box gene description
• Add description of Source on DB