Implement files on chip menu

[dannystaple]

It should have the following functions:

• Show space remaining on the device.
• List of files in the file system.
• Rename.
• Remove
• Upload
• Download

Make this either a visual lightbox popup - or a panel. The panel in a tab may work with the current visual style and be easier to implement.

[dannystaple]

This is an enhancement - although the non-implemented button on the toolbar is a bug.