Here we put Ado::Plugin::* specific configuratuon files.
The files must be named after the plugins for which they contain configuration.
A plugin Ado::Plugin::Hello will search its configuration
$app->home->rel_dir('etc/plugins/hello.conf').
The file must return a HASHREF:
(the app keyword containing the current application instance 
  is available for use)
#etc/plugins/hello.conf
{
  somekey =>'somevalue'
  #...
};

The default settings can be changed in
the common etc/ado.conf at $app->config('plugins')->{hello};
See etc/ado.conf for examples.
