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

test/Microsoft.SqlTools.ServiceLayer.TestDriver/project.json

@@ -23,7 +23,7 @@
       "imports": [
         "dotnet5.4",
         "portable-net451+win8"
-      ],
+      ]
     }
   },
   "runtimes": {