Reporting progress and dealing with internal errors

[dpvreony]

Hi

First off thank you for your efforts on this tool.

I was having an issue where my generator was throwing an exception (my fault :)) and there was a lack of detail coming from Visual Studio.

I've prepared a branch with the following changes

• Progress object is no longer null and reporting of diagnostic to stdout.
• try\catch around each file
• addition of a basic diagnostic that reports the exception during transform

This sees the following detail added to Visual Studio