Add ability to run the app outside statusbar mode

[iby]

Some might not need to use the app so often to have it in the status bar, others simply might not wanna pollute it with icons – we don't have status bar for the grab app, for a reason. Two extra options would be cool:

1. Launch the app to make a single recording.
2. Run in the background without status bar icon, launch the app to open preferences.

[natanrolnik]

I would love to see this as well. Just like mentioned in #103, using Bartender makes it extremely difficult to perform the drag and drop. Having this in the dock or as a simple window would help a lot.