Update .editorconfig

[CodeTherapist]

Update the .editorconfig with additional rules.

Advantages

• keeps the code format as defined - regardless who is contributing
• reduces PR review complexity (code formatting changes are gone)
• works for common IDE's

• Define a standard
• Extend the existing file
• Reformat solution

[rainersigwald]

We have one (untouched in 4 years), but it'd be quite reasonable to bring it up to date using the steps here.

[CodeTherapist]

@rainersigwald We could create a .editorconfig by IntelliCode that infers coding conventions from the solution. Would that work?

[rainersigwald]

Yeah, that sounds good to me. We may want to eventually standardize more with what corefx or roslyn are doing, but that can be an incremental move, if necessary.

One wrinkle I can think of: this repo has a few bits of code forked from other places. For ease of updating, those shouldn't be formatted to our conventions, but left as they were--otherwise the diffs resulting from taking a new upstream are confusing and awful. We should drop empty .editorconfig files in those directories.

[Pilchie]

We should drop empty .editorconfig files in those directories.

Editorconfig automatically chains, so instead, drop a .editorconfig with root=true.

[rainersigwald]

@livarcocc Should we think about having a standard for all of our repos and applying that here? If we don't want to push for that, I think the generate-one-from-current-usage approach sounds nice.

[Pilchie]

Most of the dotnet repos are fairly consistent already. @jaredpar, @Stoub, etc did some work to come up with https://github.com/dotnet/corefx/blob/master/Documentation/coding-guidelines/coding-style.md

[rainersigwald]

Yeah, and we shouldn't be too far off from that--at the dawn of time we used codeformatter on this repo. Just haven't been keeping up with it recently.

[livarcocc]

@rainersigwald I have been thinking about having one that's common for our whole team for a while. Feel free to drive that.