Edited Issue: Designer: COMException while adding templates during Generate/Update [1104]

__Repro steps__:
1. New Empty ADO.NET Entity Data Model
2. Add Code Generation Item
3. Update/Generate

__Unexpected result__:
* An error dialog is shown with the following message:
An exception of type 'System.Runtime.InteropServices.COMException' occurred while attempting to update from the database. The exception message is: 'A file or folder with the name 'Model1.Context.tt' already exists. Please give a unique name to the item you are adding, or delete the existing item first.'.

This issue is also encountered in these alternate scenarios:
* An error occurs while reverse engineering, and you later try to update from database
* Delete the database, Update/Genearate