Make rest API equal to api spec

Author: joshua-adams-1

rest-api-spec/src/main/resources/rest-api-spec/api/cluster.allocation_explain.json

@@ -24,19 +24,19 @@
     "params":{
       "index": {
         "type": "string",
-        "description": "Index containing the shard to be explained"
+        "description": "Specifies the name of the index that you would like an explanation for"
       },
       "shard": {
         "type": "number",
-        "description": "Shard ID to be explained"
+        "description": "Specifies the ID of the shard that you would like an explanation for"
       },
       "primary": {
         "type":"boolean",
         "description":"If true, returns explanation for the primary shard for the given shard ID"
       },
       "current_node": {
         "type": "string",
-        "description": "Node ID or the name of the node to only explain a shard that is currently located on the specified node"
+        "description": "Specifies the node ID or the name of the node to only explain a shard that is currently located on the specified node"
       },
       "master_timeout":{
         "type":"time",