Added draft istanbul json file, file integrations and access test

Author: holgerd77

src/chains/goerli.json

@@ -61,6 +61,12 @@
       "block": 0,
       "consensus": "poa",
       "finality": null
+    },
+    {
+      "name": "istanbul",
+      "block": null,
+      "consensus": "poa",
+      "finality": null
     }
   ],
   "bootstrapNodes": [

src/chains/mainnet.json

@@ -61,6 +61,12 @@
       "block": 7280000,
       "consensus": "pow",
       "finality": null
+    },
+    {
+      "name": "istanbul",
+      "block": null,
+      "consensus": "pow",
+      "finality": null
     }
   ],
   "bootstrapNodes": [

src/chains/rinkeby.json

@@ -55,6 +55,12 @@
       "block": null,
       "consensus": "poa",
       "finality": null
+    },
+    {
+      "name": "istanbul",
+      "block": null,
+      "consensus": "poa",
+      "finality": null
     }
   ],
   "bootstrapNodes": [

src/chains/ropsten.json

@@ -61,6 +61,12 @@
       "block": 4939394,
       "consensus": "pow",
       "finality": null
+    },
+    {
+      "name": "istanbul",
+      "block": null,
+      "consensus": "pow",
+      "finality": null
     }
   ],
   "bootstrapNodes": [

src/hardforks/index.ts

@@ -7,4 +7,5 @@ export const hardforks = [
   ['byzantium', require('./byzantium.json')],
   ['constantinople', require('./constantinople.json')],
   ['petersburg', require('./petersburg.json')],
+  ['istanbul', require('./istanbul.json')],
 ]

src/hardforks/istanbul.json

@@ -0,0 +1,14 @@
+{
+  "name": "istanbul",
+  "comment": "HF targeted for October 2019 following the Constantinople/Petersburg HF",
+  "eip": {
+    "url": "https://eips.ethereum.org/EIPS/eip-1679",
+    "status": "Draft"
+  },
+  "gasConfig": {},
+  "gasPrices": {},
+  "vm": {},
+  "pow": {},
+  "casper": {},
+  "sharding": {}
+}

tests/hardforks.ts

@@ -11,6 +11,8 @@ tape('[Common]: Hardfork logic', function(t: tape.Test) {
       'spuriousDragon',
       'byzantium',
       'constantinople',
+      'petersburg',
+      'istanbul',
     ]
     let c