Adding tr() for translation. Please always use tr()..

.. for text that is visible on the user interface.

Reason:
"
The tr function is the central part of the Qt internationalization system (allso called “i18n” by people who can’t handle words with more than ten letters). That’s a system for making your application available in multiple languages.
If you want your application to have multiple language support, wrap every user-visible string in your code inside a tr() function. Then Qt will use the appropriate translated string in a different language environment. Of course Qt won’t actually translate for you, you (or your translator guy) have to do that with QtLinguist.
"