Some fixes

Use the Inferrer on the Nest ConnectionSettings
Ensure consistent HashCode for ManyIndices
Use operation index/type in msearch when the request doesn't specify or when it's different from the request

Author: russcam

src/Nest/CommonAbstractions/Infer/Indices/Indices.cs

@@ -57,7 +57,8 @@ string IUrlParameter.GetString(IConnectionConfigurationValues settings)
 					var nestSettings = settings as IConnectionSettingsValues;
 					if (nestSettings == null)
 						throw new Exception("Tried to pass field name on querysting but it could not be resolved because no nest settings are available");
-					var infer = new Inferrer(nestSettings);
+
+					var infer = nestSettings.Inferrer;
 					var indices = many.Indices.Select(i => infer.IndexName(i)).Distinct();
 					return string.Join(",", indices);
 				}
@@ -81,7 +82,7 @@ public override int GetHashCode()
 		{
 			return this.Match(
 				all => "_all".GetHashCode(),
-				many => string.Concat(many.Indices).GetHashCode()
+				many => string.Concat(many.Indices.OrderBy(i => i.ToString())).GetHashCode()
 			);
 		}
 	}

src/Nest/Search/MultiSearch/MultiSearchJsonConverter.cs

@@ -22,13 +22,13 @@ public override void WriteJson(JsonWriter writer, object value, JsonSerializer s
 
 			foreach (var operation in request.Operations.Values)
 			{
-				var indices = operation.Index != null
+				var indices = request.Index == null || !request.Index.Equals(operation.Index)
 					? operation.Index
-					: request.Index;
+					: null;
 
-				var types = operation.Type != null
+				var types = request.Type == null || !request.Type.Equals(operation.Type)
 					? operation.Type
-					: request.Type;
+					: null;
 
 				var searchType = operation.RequestParameters.GetQueryStringValue<SearchType>("search_type").GetStringValue();
 				if (searchType == "query_then_fetch")