Add a main window as an alternative UI

[cadadr]

Linux desktop is at war with system tray icons, so it might be wise to add back the main window that exposes all the functionality in the AppIndicator menu.

This also pertains to #47 as I don't really know how accessible systray icons are, plus also probably to #55 .

[cadadr]

Gnome and its ilk are at war with AppIndicators, so the main UI shold probably be the main window instead. If/when DBus support is added, a few options can be added to the .desktop as well.

This is really hard to understand. Why hate AppIndicators? Even Macs retain tray and the tray applets, AFAICT. They are useful. Now, Gnome and similar did not only remove that support and require you to install some extension, it's also inaccessible as when you switch to the "top bar" with Ctrl+Alt+Tab, and tab top bar elements, they aren't read out loud, and when it comes to the pomodorino applet, it reads the entire fully qualified name multiple times, rendering it worse than useless. It also looks like menu items are not read out loud...

"R" in FOSS stands for reason...