Vmware Distributed Virtual Switches

VMware has the concept of [Distributed Virtual Switches](https://www.vmware.com/products/datacenter-virtualization/vsphere/distributed-switch.html). Currently fog doesn't support them at all and I'd like to change that. These are some very rough patches. Since I'm very new to ruby in general I'd like some feedback if this is the right path.

The only testing I've done is create a VM in the foreman and see if the VM gets the correct network backing. Known issues:
* if a DVS is inside a folder instead of directly under the DC ```get_raw_network``` will not find it