'Determines whether the given filesystem path contains a plugin.
In this base class, all sub-directories are considered plugins.
:type   plugin_path:    string
:param  plugin_path:    relative or absolute filesystem path to the
potential plugin
:rtype:                 bool
:returns:               True if the path contains a plugin'

def is_plugin(self, plugin_path):

    if (not os.path.isdir(plugin_path)):
        return False
    if ('config' not in os.listdir(plugin_path)):
        return False
    expected_config_filename = ('%s.xml' % os.path.split(plugin_path)[1])
    if (not os.path.isfile(os.path.join(plugin_path, 'config', expected_config_filename))):
        return False
    return True
