Improved candidate selection engine

[mplewis]

• Replace old candidate sorting algorithm with a more sophisticated one to support:
  • preferred tags
  • Sort modes: mostSeeders, largestFileSize
  • Minimum/maximum seeders
• New sorting engine which supports explicit item tiers
• Extract Profile into profile.ts
• Simplify quality comparison function
• Rename type attribute to mediaType for consistency
• Build and lint in CI