file viewer and editor plugin


I like to know if there is a plugin or custom code that will allow the following. Let me explain my needs:
Want to give Site Admin capabilities to edit their site's current theme. Make changes to the php, css files, edit the images of the theme and re-upload. Some sort of a file viewer and editor- in-one is probably what I'm looking for.

For security I also like to exclude other themes that they are not using. And be able to define the path or folder where that can only upload/download files.