Restrict VMs by datacenter path

[schlomo]

ATM we can restrict VM placement with ESX host name patterns.

Better would be to use paths and ressource pools as a host filter, e.g.

[vm_ressource_paths]
Datacenter/host/cluster1/webpool=.*web.*
Datacenter2/host/cluster2=.*

should force all .*web.* VMs to be created (and allowed to run) in the Ressource Pool webpool in the cluster1 Cluster. All that with the usual list syntax for multiple patterns.