Add StringValues struct for collections

[lodejard]

Streamlines all of the cases where string,string[] collections cause friction

Also has side-effect of reducing number of allocations per request

[Tratcher]

What did the CLR team have to say about this?

Also, layering. Ideally this type would be in a BCL package, not one of ours.

[Eilon]

As with many types, we should start out with our own and see where it goes.

[davidfowl]

+1

[lodejard]

I'm not sure this is necessarily a BCL/CLR asset, we certainly don't need to be gated by that for packaged code. Nothing else in HttpAbstractions and web server feature interfaces was punched down that far.

[davidfowl]

@Tratcher is concerned because of the layering of WebListener. The lower layer doesn't depend on anything except bcl types today

[Eilon]

WebListener is a DNX-only component in practice, but either way, having it depend on another package is really not so bad.

[Tratcher]

@lodejard Do you have your prototype code in a branch? Or paste it here?

[lodejard]

yep, https://github.com/aspnet/HttpAbstractions/tree/lodejard/stringvalues