Schema Updates for 10/22

[charlietaylor98]

• Metadata section that includes year, song title, artist, featured artist(s), and album
• Constrain @tone attribute values to "positive", "negative", or "neutral"
• Constrain @mood attribute values to the following:
  1. Hopeful
  2. Energetic
  3. Cynical
  4. Apathetic
  5. Empathetic
  6. Determined
  7. Angry
  8. Sad
  9. Happy
  10. Confident
  11. Anxious
  12. Ambiguous
• Add an optional <topic> parent of <line> with an @type attribute, which takes the following values:
  1. Drugs
  2. Death
  3. Family
  4. Religion
  5. Money
  6. Poverty
  7. Wealth
  8. Violence
  9. Social issues
  10. Gangs
  11. Ambiguous
• Differentiate between verses, choruses, intros, and outros