Enable terminal width detection to improve output readability

Terminal width defaults to 80 characters, and template.format() adapts to this width or the detected width.

Note that template.format() has a larger number of arguments to adapt to terminal width.

Including self.izv.reporter.set_terminal_width() in test_izverifier.py makes these changes the default for the created instance of IzVerifier. If this line is removed, width will stay at 80 until the set_terminal_width function is called.