Add shard_size support to TermStats facet

Author: Jakub Stachowski

src/Nest/DSL/Facets/TermsStatsFacetDescriptor.cs

@@ -34,6 +34,9 @@ public interface ITermsStatsFacetRequest : IFacetRequest
 		[JsonProperty(PropertyName = "size")]
 		int? Size { get; set; }
 
+		[JsonProperty(PropertyName = "shard_size")]
+		int? ShardSize { get; set; }
+
 		[JsonProperty(PropertyName = "params")]
 		[JsonConverter(typeof (DictionaryKeysAreNotPropertyNamesJsonConverter))]
 		Dictionary<string, object> Params { get; set; }
@@ -48,6 +51,7 @@ public class TermsStatsFacetRequest : FacetRequest, ITermsStatsFacetRequest
 		public TermsStatsOrder? Order { get; set; }
 		public string Lang { get; set; }
 		public int? Size { get; set; }
+		public int? ShardSize { get; set; }
 		public Dictionary<string, object> Params { get; set; }
 	}
 
@@ -69,6 +73,8 @@ public class TermsStatsFacetDescriptor<T> : BaseFacetDescriptor<TermsStatsFacetD
 
 		int? ITermsStatsFacetRequest.Size { get; set; }
 
+		int? ITermsStatsFacetRequest.ShardSize { get; set; }
+
 		Dictionary<string, object> ITermsStatsFacetRequest.Params { get; set; }
 
 		public TermsStatsFacetDescriptor<T> KeyField(Expression<Func<T, object>> objectPath)
@@ -113,6 +119,11 @@ public TermsStatsFacetDescriptor<T> Language(string language)
 			Self.Lang = language;
 			return this;
 		}
+		public TermsStatsFacetDescriptor<T> ShardSize(int shardSize)
+		{
+			Self.ShardSize = shardSize;
+			return this;
+		}
 		public TermsStatsFacetDescriptor<T> Size(int size)
 		{
 			size.ThrowIfNull("size");