auto recognize and add top 21 external nodes

[leordev]

It's possible to recognize and auto-add in Windshield all the BPs that created the bp.json file in their root directory of the registered bp address.

Instructions:
http://eosportal.io/help#modifying-meta-data
https://github.com/EOSPortal/bp-info-standard

Example:
https://www.cypherglass.com/bp.json

(The reason for doing that is to detect if 7 main bp nodes are off or forks)