Fix document selectors in remote scenarios

[Xanewok]

Closes #773
Closes #706 (apart from autocompletion, this should be improved on separately)

cc @jannickj since this touches on patterns again - turns out RelativePatterns don't work properly in remote sessions, so I fell back on using fs paths from URIs.

Tested on both Xubuntu 19.10 and Windows 10 (Remote WSL + SSH on Xubuntu), including other folders like D:\ and so far so good.

[Xanewok]

I'll merge this to cut a release now before Monday hits in full swing.

[jannickj]

Patterns is a real headache, I hope you've found the secret command :D

[austenstone]

I tested RLS 0.7.4 and it works much better in WSL2.
Autocomplete still doesn't work for me except for some things. Like a function I write.
No rust language auto complete for basic types.

Sadly I think I'm going to have to stick to Windows for now.

[jannickj]

@astone2014 Yeah, I think it's probably to do with how RLS is running, it would probably make sense to implement a proper WSL setup.