Make it easier to see the current metadata in MAT
This is a recommendation from the 1st Tails UX testing session.
In MAT the metadata information of files doesn't seem to be easily accessible as it requires the user to guess that double-clicking will bring up this info.
Add a "Display" or "Analyze" button to display current metadata?
(from redmine: created on 2014-06-22, relates #7684)