Language Server Protocol support

The current implementation of JDT.LS supports most of Language Server Protocol v3, as described below :

Message	Supported
↩️ initialize	✔
↩️ shutdown	✔
➡️ exit	✔
➡️ $/cancelRequest	✔
⬅️ window/showMessage	✔
↪️ window/showMessageRequest	✔
⬅️ window/logMessage	✔
⬅️ telemetry/event	✘
➡️ window/didChangeConfiguration	✔
➡️ window/didChangeWatchedFiles	✔
⬅️ textDocument/publishDiagnostics	✔
➡️ textDocument/didChange	✔
➡️ textDocument/didClose	✔
➡️ textDocument/didOpen	✔
➡️ textDocument/didSave	✔
↩️ textDocument/completion	✔
↩️ completionItem/resolve	✔
↩️ textDocument/hover	✔
↩️ textDocument/signatureHelp	✘
↩️ textDocument/references	✔
↩️ textDocument/documentHighlight	✔
↩️ textDocument/documentSymbol	✔
↩️ textDocument/formatting	✔
↩️ textDocument/rangeFormatting	✔
↩️ textDocument/onTypeFormatting	✘
↩️ textDocument/definition	✔
↩️ textDocument/codeAction	✔
↩️ textDocument/codeLens	✔
↩️ codeLens/resolve	✔
↩️ textDocument/documentLink	✔
↩️ documentLink/resolve	✔
↩️ textDocument/rename	✘

But JDT.LS also enhances the default Language Server Protocol by adding specific messages