#318 Qt: change GUI name (on Mac OS X)

[Mojca Miklavec]

Must be a trivial change, low priority: I would like to request renaming "gnuplot_qt" window into something more descriptive and more like human-readable application name. Even if that is just "Gnuplot" or "Gnuplot (Qt)" or something along the lines. I'm only talking about the name as seen by GUI, not about executable filename.