Correctly infer the Elasticsearch type from the CLR type

This fixes discrepancies between how C# types compare to Java types as documented in https://msdn.microsoft.com/en-us/library/ms228360(v=vs.90).aspx and https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html. Fixes issue #1643
Add additional unit tests for inferred types

Author: russcam

Diff for: src/Nest/Resolvers/Writers/TypeMappingWriter.cs

@@ -280,27 +280,29 @@ private string GetElasticsearchType(FieldType? fieldType)
 				switch (propertyType.Name)
 				{
 					case "Int32":
-					case "UInt32":
+					case "UInt16":
 						return FieldType.Integer;
 					case "Int16":
-					case "UInt16":
-						return FieldType.Short;
 					case "Byte":
+						return FieldType.Short;
 					case "SByte":
 						return FieldType.Byte;
 					case "Int64":
-					case "UInt64":
+					case "UInt32":
 						return FieldType.Long;
 					case "Single":
 						return FieldType.Float;
 					case "Decimal":
 					case "Double":
+                    case "UInt64":
 						return FieldType.Double;
 					case "DateTime":
+                    case "DateTimeOffset":
 						return FieldType.Date;
 					case "Boolean":
 						return FieldType.Boolean;
-					case "Guid":
+                    case "Char":
+                    case "Guid":
 						return FieldType.String;
 				}
 			}

Diff for: src/Tests/Nest.Tests.Unit/Core/AttributeBasedMap/AllTypesTest.cs

@@ -18,8 +18,17 @@ public class AllTypes
 			public long LongField { get; set; }
 			public float FloatField { get; set; }
 			public double DoubleField { get; set; }
-			public DateTime DateField { get; set; }
-			public bool BoolField { get; set; }
+            public decimal DecimalField { get; set; }
+            public SByte SignedByteField { get; set; }
+            public UInt64 UnsignedLongField { get; set; }
+            public UInt16 UnsignedShortField { get; set; }
+            public UInt32 UnsignedIntegerField { get; set; }
+			public DateTime DateTimeField { get; set; }
+            public DateTimeOffset DateTimeOffsetField { get; set; }
+            public bool BoolField { get; set; }
+            public string StringField { get; set; }
+            public Guid GuidField { get; set; }
+            public char CharField { get; set; }
 		}
 
 		[Test]

Diff for: src/Tests/Nest.Tests.Unit/Core/AttributeBasedMap/TestAllTypes.json

@@ -1,30 +1,57 @@
 {
-  "alltypes": {
-    "properties": {
-      "integerField": {
-        "type": "integer"
-      },
-      "shortField": {
-        "type": "short"
-      },
-      "byteField": {
-        "type": "byte"
-      },
-      "longField": {
-        "type": "long"
-      },
-      "floatField": {
-        "type": "float"
-      },
-      "doubleField": {
-        "type": "double"
-      },
-      "dateField": {
-        "type": "date"
-      },
-      "boolField": {
-        "type": "boolean"
-      }
+    "alltypes": {
+        "properties": {
+            "integerField": {
+                "type": "integer"
+            },
+            "shortField": {
+                "type": "short"
+            },
+            "byteField": {
+                "type": "short"
+            },
+            "longField": {
+                "type": "long"
+            },
+            "floatField": {
+                "type": "float"
+            },
+            "doubleField": {
+                "type": "double"
+            },
+            "decimalField": {
+                "type": "double"
+            },
+            "signedByteField": {
+                "type": "byte"
+            },
+            "unsignedLongField": {
+                "type": "double"
+            },            
+            "unsignedShortField": {
+                "type": "integer"
+            },            
+            "unsignedIntegerField": {
+                "type": "long"
+            },
+            "dateTimeField": {
+                "type": "date"
+            },         
+            "dateTimeOffsetField": {
+                "type": "date"
+            },
+            "boolField": {
+                "type": "boolean"
+            },
+            "stringField": {
+                "type": "string"
+            },
+            "guidField": {
+                "type": "string"
+            },            
+            "charField": {
+                "type": "string"
+            }
+        }
     }
-  }
 }