Update documentation for work in #502

Update the documentation for work done to solve #502 (closed).

• Multiple charts for the globalization of `minio.enabled.
• Registry for the move of storage from map to secret (containing YAML block)
• Unicorn/Sidekiq/globals for the migration of lfs/artifacts/uploads to global.appConfig
  • Updated explanation of connection.
  • One shared entry, instead of repeating three times. Blocks are effectively identical.

cc @twk3 @marin @joshlambert @balasankarc