Virtual resource support

[adepretis]

It would be great if this module would use virtual resources to define and collect standard jails. Right now you have to pass all bundled jails when declaring the fail2ban class, e.g.:

class { '::fail2ban':
  jails => ['ssh', 'proftpd', ...]
  ...

It would be nicer to exclude the default jails from the bundled config file templates and make fragments that can be declared and collected like e.g.

class { '::fail2ban':
  dotheotherthings
}

@fail2ban::bundled { 'ssh':
  ...
}

@fail2ban::bundled { 'proftpd':
  ...
}

Fail2ban::Bundled <<| |>>

This way you can couple fail2ban more conveniently with services instead of having to think about modifying the class declaration anytime you add a service to a system. Unfortunately I don't have the time right now to write a PR, but maybe someone else thinks this is a good idea too and likes to create a PR.