New unit tests for String.Format and number-type.ToString() (#146)

***NO_CI***

Author: edleno2

Tests/NFUnitTestArithmetic/NFUnitTestArithmetic.nfproj

@@ -27,6 +27,7 @@
     <RunSettingsFilePath>$(MSBuildProjectDirectory)\nano.runsettings</RunSettingsFilePath>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="UnitTestFormat.cs" />
     <Compile Include="UnitTestArithmeticTest1.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="UnitTestArithmeticTest2.cs" />