Add support for handling moved files

[Pajn]

When a file is moved or renamed many languages would need to update import paths and maybe even symbol names.
I can't see a good way to handle that with the current API, would it be possible to add a request for that?

[dbaeumer]

Yes, it makes sense to provide a move refactoring request.

[fbricon]

We're gonna need that feature for Java support (eclipse-jdtls/eclipse.jdt.ls#363). Any way to prioritize this? cc @aeschli @akaroml @tsmaeder

[dbaeumer]

The best way to speed this up is to provide a PR. But this needs to happen in the protocol, the node libraries and very likely in VS Code as well.

[dbaeumer]

Closing in favor of #272