#1775 Display translated percentage on Project files dialog

[Porrumentzio]

Sometimes users have a lot of files in a project and want to know which are already translated and which no in an easy way. In v5.7.1 though there is no way to see that but to enter each file one by one.
Thus, it would be great to have a column for translated/total segments in the Project files dialog, just the same info displayed on the bottom right corner when a file is open.

For being visually more attractive, I would add a bar that fills up and changes the filling color (less translated red - more translated green).