Adapt to newer Omnisharp-roslyn including direct support for LSP

[mickaelistria]

See OmniSharp/omnisharp-roslyn#968 (comment)
OmniSharp-roslyn now directly support LSP with ./run -stdio -lsp. It's been tried successfully on Eclipse IDE with aCute. Using it allows to get rid of a bunch of dependencies such as nodejs and of some indirections.

[bmicklea]

@tsmaeder - is this a licensing issue? I didn't think the omnisharp LSP was truly FOSS...

[mickaelistria]

I think it's truly OSS, at least OSS enough to be approved in an Eclipse.org project (Eclipse aCute got a CQ approved for Omnisharp-Roslyn). License is MIT, it uses mono (MIT) too and dotnet core to provide its features.

[mickaelistria]

https://dev.eclipse.org/ipzilla/show_bug.cgi?id=15334 is the Eclipse.org CQ that allowed Eclipse aCute to ship Omnisharp-Roslyn.

@mickaelistria I will look at it. Thanks for bringing this up

Tried it and failed. Somehow, Che client refuses to work: eclipse-che/che#9351