Add support for numeric_resolution to date mapping

Closes #1449

Author: gmarz

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

@@ -94,5 +94,11 @@ public DateMappingDescriptor<T> DocValues(bool docValues = true)
 			this._Mapping.DocValues = docValues;
 			return this;
 		}
+
+		public DateMappingDescriptor<T> NumericResolution(NumericResolutionUnit unit)
+		{
+			this._Mapping.NumericResolution = unit;
+			return this;
+		}
 	}
 }

src/Nest/Domain/Mapping/Types/DateMapping.cs

@@ -41,5 +41,8 @@ public DateMapping():base("date")
 
 		[JsonProperty("doc_values")]
 		public bool? DocValues { get; set; }
+
+		[JsonProperty("numeric_resolution")]
+		public NumericResolutionUnit NumericResolution { get; set; }
 	}
 }

src/Nest/Enums/NumericResolutionUnit.cs

@@ -0,0 +1,19 @@
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+
+namespace Nest
+{
+	[JsonConverter(typeof(StringEnumConverter))]
+	public enum NumericResolutionUnit
+	{
+		[EnumMember(Value = "milliseconds")]
+		Milliseconds,
+		[EnumMember(Value = "seconds")]
+		Seconds
+	}
+}

src/Nest/Nest.csproj

@@ -406,6 +406,7 @@
     <Compile Include="Enums\GeoShapeRelation.cs" />
     <Compile Include="Enums\HighlighterType.cs" />
     <Compile Include="Enums\NormsLoading.cs" />
+    <Compile Include="Enums\NumericResolutionUnit.cs" />
     <Compile Include="Enums\RangeExecution.cs" />
     <Compile Include="Enums\RoutingAllocationEnableOption.cs" />
     <Compile Include="Enums\ScriptLang.cs" />

src/Tests/Nest.Tests.Unit/Core/Map/Properties/DateProperty.json

@@ -11,7 +11,9 @@
         "boost": 1.3,
         "null_value": "1986-03-08T00:00:00",
         "include_in_all": true,
-        "ignore_malformed": true
+        "ignore_malformed": true,
+        "doc_values": true,
+        "numeric_resolution": "seconds"
       }
     }
   }

src/Tests/Nest.Tests.Unit/Core/Map/Properties/PropertiesTests.cs

@@ -92,6 +92,8 @@ public void DateProperty()
 						.PrecisionStep(4)
 						.Store()
 						.Boost(1.3)
+						.DocValues()
+						.NumericResolution(NumericResolutionUnit.Seconds)
 					)
 				)
 			);