Respect Lua.trace.server=verbose to enable verbose LSP logging #131

I'm trying to read the LSP traffic when using VSCode.
Other languages support a <langId>.trace.server setting, see https://code.visualstudio.com/api/language-extensions/language-server-extension-guide#logging-support-for-language-server
Setting it to "verbose" should log all JSON-RPC LSP message.

The Lua server log has some info but not all and I'd like to avoid using something that's specific to the language server here.