Tray icon support

Calculator can be useful many times a day and it would be nice to be able to minimize the Speedcrunch, so it doesn't show in the list of running programs in task bar.

Also, would be nice to be able to make it to never show in the taskbar even when I'm using it.

And when I press on the minimize button or close button in the top right corner of the window, instead of closing the window and exit program - minimize it to tray instead.