Support for USB accessory URIs

If a USB accessory is attached and we have no application that supports it,
display a dialog offering the user the option to visit the accessory's website
if the accessory has a URI.

Bug: 4073248

Change-Id: I30e2a802493fb6e203532a7f79402379c40bc3b8
Signed-off-by: Mike Lockwood <lockwood@android.com>