Add Scalar quantity (#889)

e.g. Scalar.FromAmount(1.5).

Author: Joe-houghton

Common/UnitDefinitions/Scalar.json

@@ -0,0 +1,19 @@
+{
+  "Name": "Scalar",
+  "BaseUnit": "Amount",
+  "XmlDoc": "A way of representing a number of items.",
+  "Units": [
+    {
+      "SingularName": "Amount",
+      "PluralName": "Amount",
+      "FromUnitToBaseFunc": "x",
+      "FromBaseToUnitFunc": "x",
+      "Localization": [
+        {
+          "Culture": "en-US",
+          "Abbreviations": [ "" ]
+        }
+      ]
+    }
+  ]
+}

UnitsNet.NumberExtensions.Tests/GeneratedCode/NumberToScalarExtensionsTest.g.cs

@@ -0,0 +1,32 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by \generate-code.bat.
+//
+//     Changes to this file will be lost when the code is regenerated.
+//     The build server regenerates the code before each build and a pre-build
+//     step will regenerate the code on each local build.
+//
+//     See https://github.com/angularsen/UnitsNet/wiki/Adding-a-New-Unit for how to add or edit units.
+//
+//     Add CustomCode\Quantities\MyQuantity.extra.cs files to add code to generated quantities.
+//     Add UnitDefinitions\MyQuantity.json and run generate-code.bat to generate new units or quantities.
+//
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+// Licensed under MIT No Attribution, see LICENSE file at the root.
+// Copyright 2013 Andreas Gullberg Larsen ([email protected]). Maintained at https://github.com/angularsen/UnitsNet.
+
+using System;
+using Xunit;
+
+namespace UnitsNet.Tests.CustomCode
+{
+    public class ScalarTests : ScalarTestsBase
+    {
+        // Override properties in base class here
+        protected override double AmountInOneAmount => 1;
+        protected override bool SupportsSIUnitSystem => false;
+       
+    }
+}