Integrate YAKINDU Solidity Language Server

[flantony]

The YAKINDU Solidity language server (https://github.com/Yakindu/solidity-ide) provides some features that are not yet implemented/can be improved.

Most noteworthy:

• grammar based code completion
• code formatter according to the Solidity style guide
• quick fixes for compiler warnings/errors (could be extended to Linter issues as well)
• semantic rename refactorings (instead of text replace)
• semantic code navigation

We could add the YAKINDU language server as an alternative backend or delegate to it for certain protocol aspects.

[0mkara]

@flantony I try to have a look into the YAKINDU Solidity Language Server Integration. I see some extension examples in the GitHub repository. But I find no clue on what package or binary I should install to use the language server. Can you give us some more into on the integration process?