verify_pnp_config_v2 should support Icinga 2

[dnsmichi]

I haven't looked deeply into the code yet but I would suggest the following:

• Add a new product called "icinga2"
• Modify the user detection in get_product() for icinga2
• Only allow "bulk+npcd" as mode for icinga2
• Special check just for performance data feature being enabled
• Optionally fetch the path from the PerfdataWriter feature (icinga2 object list --type PerfdataWriter) and compare it with the npcd.cfg
• Check whether EnablePerfdata is globally enabled or not (icinga2 object list --type IcingaApplication)
• Optional: Connect against a running instance using the REST API and read the required attributes (similar to status.dat and objects.cache opt-in)

I'll look into a patch but it might take a while. If others want to look into that, much appreciated :)