[v2] Add PeerDB file name and version (#2)

Author: jcxldn

constants.json

@@ -1,8 +1,12 @@
 {
   "this_loc": "https://raw.githubusercontent.com/mdmulti/constants/master/constants.json",
-  "version" : 1,
+  "version" : 2,
   "mdmc_version": 3,
   "mdms_version": 1,
+  "peerdb_file": {
+    "name": "peerdb.mdm.json",
+    "version": 1
+  },
   "oid": {
     "base": "1.3.6.1.4.1.54622.0.1"
   },