This allows the admin interface to see which plugins are registered and
enabled. Enabled is a flag that is set in the setup() method of the
plugin. This gives the plugin developer a chance to disable the plugin
if something isn't right at setup time. This allows aprsd to ignore
plugins that are registered but not emabled.
This patch updates the APRSDPluginBase class to include
standard methods for allowing plugins to create, start, stop
threads that the plugin might need/use. Also update the aprsd-dev
to correctly start the threads and stop them for testing plugin
functionality.
Also added more unit tests and fake objects for unit tests.
