Automatic default selection of virtualization type depending on bootstrap data

Fuel environments may contain nodes with different virtualization type. It is already possible case, though not really practical one, when we can have multiple nodes with kvm, and multiple with qemu only available. For further partners integrations we may have more virtualization types, for example xen or esx.

Consequently, we need to have:
a) automatic determination of hypervisor type for node where possible. However it is likely that we need to leave an ability to specify another type if needed
b) force user to choose virtualization type for node where it has not been detected automatically for some reason
c) We need to add an ability to group nodes by virtualization type
d) user should be able to set virt type for group of nodes, not only one-by-one
e) if both qemu and kvm are available, it should be kvm by default

Status can be taken from 'grep -Eq 'svm|vmx' /proc/cpuinfo ; echo $?'