Review internal pages and links to docs

[giohappy]

• https://geonode.org/user_features/
  • fix links to documentation sections
• https://geonode.org/dev_features/
  • Rewrite the "Bootstrap and jQuery" section, turning into something about GeoNode MapStore Client, MapStore, React, etc.
  • fix links to documentation sections
• https://geonode.org/admin_features/
  • fix links to documentation sections