Convert raw header to JSON

- Enables parsing values off of header via Postgres migration

db/migrations/1531758090_create_headers_table.up.sql

@@ -2,7 +2,7 @@ CREATE TABLE public.headers (
   id                    SERIAL PRIMARY KEY,
   hash                  VARCHAR(66),
   block_number          BIGINT,
-  raw                   bytea,
+  raw                   JSONB,
   eth_node_id           INTEGER,
   eth_node_fingerprint  VARCHAR(128),
   CONSTRAINT eth_nodes_fk FOREIGN KEY (eth_node_id)

db/schema.sql

@@ -2,8 +2,8 @@
 -- PostgreSQL database dump
 --
 
--- Dumped from database version 10.5
--- Dumped by pg_dump version 10.5
+-- Dumped from database version 10.3
+-- Dumped by pg_dump version 10.3
 
 SET statement_timeout = 0;
 SET lock_timeout = 0;
@@ -1097,7 +1097,7 @@ CREATE TABLE public.headers (
     id integer NOT NULL,
     hash character varying(66),
     block_number bigint,
-    raw bytea,
+    raw jsonb,
     eth_node_id integer,
     eth_node_fingerprint character varying(128)
 );