chg: [vulnerability] vulnerability is is now a vulnerability type

The vulnerability type is an official CVE number.

We might need to add in the future a new attribute in the object
for non-CVE id of a vulnerability or adding other id type in the object.

This commit fixes #234

objects/vulnerability/definition.json

@@ -32,7 +32,7 @@
     },
     "id": {
       "description": "Vulnerability ID (generally CVE, but not necessarely). The id is not required as the object itself has an UUID and the CVE id can be update or assigned later.",
-      "misp-attribute": "text",
+      "misp-attribute": "vulnerability",
       "multiple": true,
       "ui-priority": 0
     },
@@ -94,5 +94,5 @@
     "id"
   ],
   "uuid": "81650945-f186-437b-8945-9f31715d32da",
-  "version": 6
+  "version": 7
 }