LSP for CodeCompass

[Kalfou]

LSP handler and C++ LSP plugin added with some utility functions and a common interface for LSP plugins.

Enhances #335.

[intjftw]

I haven't checked the entire cpplspservice.cpp class, but I looked through all the other ones. I'm starting the review so @Kalfou can start adding fixes.

[intjftw]

I found the code generally nice and clean, and architecturally correct. I have two more small change requests.

[intjftw]

@Kalfou please write a short description of the LSP options in the README, and build and install directions in the README of the plugin.

Considering the plugin, I only have one issue: currently, the package.json file contains default values for CodeCompass properties (project path, name, webserver port number etc.). This solution is quite inflexible, and increases the chance of user errors. In my opinion, the plugin should be able to handle several projects. Also, the json file or the README should be complemented with a template on how to add new project properties to the file.

[mcserep]

@Kalfou I have fixed and refactored the outdated CI in #596, please rebase this PR onto master (or merge it), so the pipeline can be executed properly.

[Kalfou]

Hi,
Is there anything that still needs to be done to make this merge ready?

[mcserep]

Sorry for the late response @Kalfou and thanks for updating the PR according to the reviews. I think this is ready for merge 🚀

It would be also nice to publish the VS Code LSP plugin somewhere, as currently it is only available in private repository on the ELTE FI Gitlab server.
I think it should either be added to this repo (in a separate PR) or maybe a new repo could be created for LSP plugins (with the possible future work towards other IDEs).