Code coverage improvements (#121)

These are test-only changes to improve code coverage so I'll merge directly.  Please review the commit and I'll pickup those changes in the next iteration.

* Add integration test batch file

* Exclude Linux and MacOS from Windows code coverage builds

* Enable code coverage for test driver e2e tests

* Use the windows only build for code coverage runs

src/Microsoft.SqlTools.ServiceLayer/Credentials/OSX/OSXCredentialStore.cs

@@ -10,6 +10,9 @@ using Microsoft.SqlTools.ServiceLayer.Utility;
 
 namespace Microsoft.SqlTools.ServiceLayer.Credentials.OSX
 {
+
+#if !WINDOWS_ONLY_BUILD
+
     /// <summary>
     /// OSX implementation of the credential store
     /// </summary>
@@ -155,4 +158,8 @@ namespace Microsoft.SqlTools.ServiceLayer.Credentials.OSX
             }
         }
     }
-}
+
+#endif
+
+}
+