(Optional) Output Window Service

This pull request shows how I would implement the Output Window support using the [Output Window Service](http://tunnelvisionlabs.github.io/vsbase/docs-master/html/9452cedb-1942-4d9b-b911-7ef1e882f421.htm) functionality provided by the [Base Extensions Library for Visual Studio](https://github.com/tunnelvisionlabs/vsbase) project. The pull request contains two commits:

1. The first commit is the minimum commit to use the feature. End users will not face any issues with deploying the Output Window Service functionality, but developers on this project are expected to install the debugging support extension before working in the experimental hive.

2. The second commit provides clean and clear error message and instructions for installing the Output Window Service for debugging purposes, and selectively disables only the Output Window functionality when it is missing.