Replace pd-gui -> nw in the ForceQuit actions, which is the proper name of the GUI program on Linux.

These aren't going to be substituted in desktop actions anyway, because
desktop actions are supposed to be chosen from a menu, not being dragged to.

We do this to prevent extra arguments to be passed from the DE.

At least on KDE, it seems that the desktop file itself gets passed if the
action is invoked by right-clicking the icon on the desktop (this doesn't
happen with panel icons). Maybe this is a bug in KDE, but we need to prevent
this, because otherwise Purr Data tries to open the desktop file as a patch,
which of course will cause a bunch of ugly error messages in the main window.

made shortcuts more flexible in terms of startup (not forcing JACK, which will help on setups that don't want/need JACK backend), as well as providing intelligent menu shortcuts for ALSA and JACK

improved icons and added ability to open patches by dragging and dropping or double-clicking on the patches within nautilus