Use OnException event to display stack traces for exceptions.

[cgranade]

This PR uses the OnException event introduced by microsoft/qsharp-runtime#157 to format exception stack traces as an HTML details element, making it easier to hide extraneous information while still allowing interested users to drill down through stack traces.

Collapsed:

Expanded:

When stack traces contain more useful information (e.g.: source locations for library functions and operations), that information is formatted as a hyperlink using @vadym-kl's logic for finding best source locations added in microsoft/qsharp-runtime#79.

This PR is marked as draft in lieu of API docs (#98) and feedback on the UI design, as well as the completion of microsoft/qsharp-runtime#157.

[anpaz]

The magic for the other simulators (%toffoli, %estimate) should get the same treatment.
How does it look when this is triggered on Python?

[cgranade]

@anpaz-msft: Thanks for the feedback! I've confirmed that the Python output is unaffected, since the changes here set up result encoders for both text/plain and text/html (see screenshot below). I've also added the same logic to %toffoli and %estimate. Once I've finished API docs, I'll mark this as being ready. Thanks!

[vxfield]

I've been following this for two week and the code is good.
Suggested (future) improvements:

1. Create a IResultEncoder and use some reflection for registering/invoking the encoders.
2. Create a generic encoder XsltResultEncoder<> : IResultEncoder, use a Xslt to transform the object to HTML or Text. The advantage for that is less code to maintain and make it more declarative using the templates.
   I did some tests and it's also working fine.

[cgranade]

Thanks for the review, @vxfield, and for the suggestions for future improvements! I think that could work great for improving how result encoders work going forward.