Removing a magic value in favor of a variable

Hi all,

I just ran into a problem with a magic value at plugins/kolab_tags/lib/kolab_tags_backend.php:48
When creating more than 100 tags per folder they just disappear from the webinterface (even though they are created successfully on the server). While changing the magic value fixed the problem for me, I'd like to create a PR that changes the magic value to a variable (e.g. $config['kolab_tags_per_folder'] = 100). Unfortunately, I failed to access the global configuration from class kolab_tags_backend. Other plugins use something like $this->rc->config->get('config_name').

I hope someone can give me a few hints on how to include the global configuration.

Best,
Kevin