title: HTML file field with multiple files selection and add/remove files functionality
body: <p>I need to implement a HTML form for submitting data and uploading multiple small files (number of files can vary from 1 to 30). In HTML5, there is a <code>multiple</code> attribute that allows multiple selection in one file field. I am wondering if it is possible to allow users to add/remove a single file to/from current selection. HTML5 solution is oaky, non-cross-browser solution is okay, as long as it supports Firefox.</p>