Add reference to new dependency System.ComponentModel.DataAnnotations in test project.

Author: jforsell

test/SymphonyOSS.RestApiClient.Tests/SymphonyOSS.RestApiClient.Tests.csproj

@@ -51,6 +51,7 @@
       <Private>True</Private>
     </Reference>
     <Reference Include="System" />
+    <Reference Include="System.ComponentModel.DataAnnotations" />
     <Reference Include="System.Core" />
     <Reference Include="System.Xml.Linq" />
     <Reference Include="System.Data.DataSetExtensions" />