Download all folder files under .folder-edit-button node

In MDL-51306 we added the option to bulk download all files within a folder, we added the new button under a container with .folder-edit-button CSS class, the name of the class references edit button but now it contains more stuff than that. We are not going to die if we don't fix this, but in case anyone is interested I can think of some alternatives:

1. Rename folder-edit-button (with a note in theme/upgrade.txt)
2. Add a new container for download folder with a new css selector, probably same styling than .folder-edit-button
3. Do nothing and close this