added completion mapping example

Author: Mpdreamz

src/Nest.Tests.Unit/Core/Map/FluentMappingFullExampleTests.cs

@@ -234,6 +234,15 @@ public void MapFluentFull()
 						.TreeLevels(2)
 						.DistanceErrorPercentage(0.025)
 					)
+					.Completion(s=>s
+						.Name(p=>p.Name)
+						.IndexAnalyzer("standard")
+						.SearchAnalyzer("standard")
+						.MaxInputLength(20)
+						.Payloads()
+						.PreservePositionIncrements()
+						.PreserveSeparators()
+					)
 				)
 			);
 

src/Nest/Domain/Mapping/Descriptors/CompletionMappingDescriptor.cs

@@ -36,19 +36,19 @@ public CompletionMappingDescriptor<T> IndexAnalyzer(string name)
             return this;
         }
 
-        public CompletionMappingDescriptor<T> Payloads(bool payloads)
+        public CompletionMappingDescriptor<T> Payloads(bool payloads = true)
         {
             this._Mapping.Payloads = payloads;
             return this;
         }
 
-        public CompletionMappingDescriptor<T> PreserveSeparators(bool preserveSeparators)
+        public CompletionMappingDescriptor<T> PreserveSeparators(bool preserveSeparators = true)
         {
             this._Mapping.PreserveSeparators = preserveSeparators;
             return this;
         }
 
-        public CompletionMappingDescriptor<T> PreservePositionIncrements(bool preservePositionIncrements)
+        public CompletionMappingDescriptor<T> PreservePositionIncrements(bool preservePositionIncrements = true)
         {
             this._Mapping.PreservePositionIncrements = preservePositionIncrements;
             return this;