CHE-5154: use another implementation of the Language Server Protocol for python

[svor]

What does this PR do?

Changes an implementation of the LSP for python and adopts plugin-languageserver for using this one. The new implementation is from https://github.com/palantir/python-language-server.

New Features:

1. Error/warning markers and messages
   
2. Auto Completition
   
3. Find References
   
4. Find Definition
   
5. Hover
   

What issues does this PR fix or reference?

#5154
#4976

Changelog

Change an implementation of the LSP for python

Release Notes

We have updated the LS used for Python by the Palayton one. This new Python LS is providing a better support and analyzis of the language which allows:

1. Error/warning markers and messages
2. Auto Completion
3. Find References
4. Find Definition
5. Hover

Docs PR

[svor]

@tolusha Need to replace binaries with New Binary

[codenvy-ci]

Build success. https://ci.codenvycorp.com/job/che-pullrequests-build/2736/

[codenvy-ci]

Build success. https://ci.codenvycorp.com/job/che-pullrequests-build/2738/

[slemeur]

@svor : Could you please describe in the PR description the various benefits of having this new LS for python?

[svor]

@slemeur I've updated

[slemeur]

Thanks @svor. it is perfect.

[philipp-lein]

First ... Thanks man I' ve waiting for this feature so long and I was not able to make it work.
Well Done, I'm really happy!
I need the new python features for a presentation next week.
I've pulled the master branch and build ls-python-agent and ws-agent-war and and and...
Maybe I've forgotten a build dependency or can't it work because the binaries (https://codenvy.com/update/repository/public/download/org.eclipse.che.ls.python.binaries) not updated at the moment?

Thanks a lot

[tolusha]

@phill1234
Binaries will be updated as soon as release is done.