Allow requests to specify formatting hints.

[richardstanton]

Add optional formatting object to allow customization on how values and stack frames are displayed.

@weinand
@jacdavis @gregg-miskelly @andrewcrawley @tzwlai

[msftclas]

Hi @richardstanton, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

It looks like you're a Microsoft contributor (Richard Stanton). If you're full-time, we DON'T require a Contribution License Agreement. If you are a vendor, please DO sign the electronic Contribution License Agreement. It will take 2 minutes and there's no faxing! https://cla.microsoft.com.

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[weinand]

@richardstanton before sending a PR please create an issue that explains the protocol additions and where we can discuss it.

[richardstanton]

@weinand I created an issue for this. Sorry, I misunderstood the process for protocol changes. #84

[weinand]

@richardstanton great, thanks a lot. In VS Code we always try to have a feature discussion before a PR is created. With this we try to avoid that a PR diverges too much from our own plans and thinking.

[weinand]

@richardstanton thanks for this PR!