function UserServer(config) {
        BaseServer.call(this, config);
    }
Live preview server for user specified server as defined with Live Preview Base Url
Project setting. In a clean installation of Brackets, this is the highest priority
server provider, if defined.

Configuration parameters for this server:
- baseUrl      - Optional base URL (populated by the current project)
- pathResolver - Function to covert absolute native paths to project relative paths
- root         - Native path to the project root (and base URL)

@constructor
@param {!{baseUrl: string, root: string, pathResolver: function(string)}} config
@extends {BaseServer}