Static web resource paths in gui-editor-apex are incorrect

Many of the relative paths used in the HTML/CSS for Apex Editor are incorrect in the build, e.g. index.html references "../js/fileMenu.js" instead of "js/fileMenu.js". When the project is built, maven will package the "js" and "css" directories in the same directory as index.html.

The issue is not observed when running the Apex Editor as a jar, as Jetty server will resolve parent link above document root, e.g."../js/fileMenu.js" resolves to "/js/fileMenu.js", but it becomes troublesome if used with a proxy like nginx.