The messaging.py now is nothing but a shell that
contains a link to packets.NULL_MESSAGE to help maintain
some backwards compatibility with plugins.
Packets dataclass has fully replaced messaging objects.
This patch updates the ouput of the list-plugins command.
This also adds the ability to show the available plugins
to install that are published packages on pypi.org.
This also shows the list of installed packages from pypi.org
This patch refactors the cli to incorporate
the dev, send-message, listen commands into the main aprsd app.
This also moves the command line completion installer/show into
it's own subgroup.