Store the original argv[0] and during restart, cleanup and resign as
the window manager, then execlp(argv[0]).

This will help things like compton not draw shadows under them.

We're not sharing anything with any external programs so there's
nothing to make common anymore.

Move the action taking out of the keyboard code and allow it to be
shared with the launcher.

Add a "quit" action which can now be used by both, and add it to the
bottom of the default launcher menu.

This lets us drop the dependency on Gtk and avoids having to shell
out to an external program.

Admittedly the new launcher window has a very Xt feel to it, but
maybe we can spruce it up with some button bevels or something
later.

This avoids having to specify any default keybindings in code and if
the user has their own config file, no longer requires them to
override the default keybindings to get rid of them.