Use ExceptionTelemetry for tracking exceptions

[henkmollema]

Tracking ExceptionTelemetry instances rather than TraceTelemetry provides a nicer experience in UI's such as Visual Studio and the Azure portal.

Resolves #393

[msftclas]

@henkmollema,
Thanks for your contribution.
To ensure that the project team has proper rights to use your work, please complete the Contribution License Agreement at https://cla.microsoft.com.

It will cover your contributions to all Microsoft-managed open source projects.
Thanks,
Microsoft Pull Request Bot

[msftclas]

@henkmollema, thanks for signing the contribution license agreement. We will now validate the agreement and then the pull request.

Thanks, Microsoft Pull Request Bot

[henkmollema]

Thanks @dnduffy! Any chance this makes it into 2.1?

[dnduffy]

@henkmollema We actually had the final build for 2.1 on Wednesday and just released it today after a final test pass. However, there is talk of pushing a couple features into a 2.1.1 before 2.2 so it might not wait very long for inclusion in a stable release.

[henkmollema]

I see, no worries. Thanks!