* Refactor peer_pool.
Fix eth2_network peer counters.
Fix PeerPool do not allow to add more peers when empty space available.
* Remove unused imports.
* Add test for a bug.
* Fix eth2_network disconnect should deletePeer not release.
More PeerPool refactoring.
* Add "drop by score" ability to PeerPool.
Add tests.
Fix syncmanager queue to start from most fresh data.
* Fix endless cycle at the end of syncing process.