Feature/completion item/resolve

[krassowski]

Supersedes palantir/python-language-server#905.

• implemented new hook for resolve
• implemented resolve in jedi_completion and rope_completion
• added eager option to rope_completion and jedi_completion allow users using clients which cannot yet handle completionItem/resolve to restore to eager resolution (inside of textDocument/completions)
• added test for resolve and documentation in Jedi
• tested with development version of JupyterLab-LSP client; the client implementation was tested against reference JavaScript/TypeScript server and against the R-languageserver

[krassowski]

After the fork became detached the changes from my old fork are no longer updated despite of me updating the branch. To work around this I created a branch on my new fork of the current detached fork. If anyone is interested, it was as simple as:

cd python-language-server

# on the old fork of pyls
git add remote upstream-community git@github.com:python-lsp/python-lsp-server.git
git fetch upstream-community
git checkout develop
git merge upstream-community/develop
git checkout feature/completionItem/resolve
git rebase develop
# solve conflicts
git push -f

cd ../python-lsp-server

# on new fork of pylsp
git checkout -b krassowski-feature/completionItem/resolve develop
git push --set-upstream origin krassowski-feature/completionItem/resolve

[krassowski]

Superseded by #25.