Make the menu item title and empty text for the file license table

Having the full module title isn't as necessary in the menu item as more description if necessary, so I'd like to recommend the following two changes for a little more clarity / consistency:

1. Change the Commerce Files menu item title to "File licenses."
2. Change the empty text on that table to "No file licenses have been issued."

This will match it up to what's actually appearing on the page (a View of file license entities) and the local action link to "Add a file license" appearing at the top of the page.