Added the API definition for deleting an index

rest-api-spec/api/indices.delete.json

@@ -1,18 +1,24 @@
 {
   "indices.delete": {
-    "documentation": "",
+    "documentation": "http://www.elasticsearch.org/guide/reference/api/admin-indices-delete-index/",
     "methods": ["DELETE"],
     "url": {
       "path": "/",
       "paths": ["/", "/{index}"],
       "parts": {
         "index": {
+          "type" : "list",
+          "description" : "A comma-separated list of indices to delete; use `_all` or empty string to delete all indices"
         }
       },
       "params": {
         "index": {
+          "type" : "string",
+          "description" : "The name of the index"
         },
         "timeout": {
+          "type" : "time",
+          "description" : "Explicit operation timeout"
         }
       }
     },