Support to create custom fail2ban filters

This PR adds the possibility to create custom fail2ban filters.   
Filters are provided as a hash with a filterregex and a ignoreregex.
For each filter a config file will be created in the filters.d directory.

Usage:
```
default['fail2ban']['filters'] = {
  'nginx-noscript' => { 'filterregex' = ['^<HOST> -.*GET.*(\.php|\.asp|\.exe|\.pl|\.cgi|\scgi)'] }
}
```