Eclipse LSP client

[alanz]

Eclipse has LSP support and there is a java client for it.

Use these (or any other resources) to build a haskell-ide-engine client/plugin for eclipse.

[alanz]

cc @DanielG

[nponeccop]

http://eclipsefp.github.io/ (now unmaintained as @JPMoresmau doesn't have time) had a fairly rich feature set. So we can just revive EclipseFP and use LSP4E when possible.

From what I see, LSP4E lets you configure arbitrary language servers, so it's exactly like LanguageClient for neovim.

[alanz]

Sounds good. I tried firing up an eclipse earlier today, by my java skills have left me.

What should happen is that the client side is trivial, in the form of saying what kind of files it handles and how to launch the server. That is the whole point of the protocol.