Sync only missing blocks on cold import

= Add eth_node_fingerprint to block that can be imitated by both hot and cold imports
- Only sync missing blocks (blocks that are missing or don't share a fingerprint) on cold import
- Set block is_final status after import

db/schema.sql

@@ -83,7 +83,8 @@ CREATE TABLE public.blocks (
     miner character varying(42),
     extra_data character varying,
     reward double precision,
-    uncles_reward double precision
+    uncles_reward double precision,
+    eth_node_fingerprint character varying(128) NOT NULL
 );