Coin API: Add information about the VM/host that runs each workitem

This is mostly suitable for GET /taskWorkItems. It should list details about where each workitem was run and the properties of the host/VM

• IP address
• agent port
• agent ID
• CPU cores
• RAM
• type: VM or real hardware - I'm not sure if it's meaningful to have different types for different VMs, for example opennebula-vm vs parallels-vm

If it is a VM, we should have some extra details

• hypervisor host
• VM template image

If it's a real hardware host then the hostname and I don't know what other information might apply there.

More data possibly. Coin should provide all information it has.