fixes #843 - show more virtual guests information

added html view for guests
moved common methods into the virt plugin

fixes #835 - allow to delete virtual guests

added JSON output to guests
Added Guest model
Added confirmation before power cycle
Added Deletion option to guests

fixes #723 - Hypervisor details page

This also include basic functionality to power on/off guests

fixes #582 - Foreman should not fail if libvirt ruby binding are not installed

fixed broken tests

added default order and paginations which
fixes #721
fixes #688

fixes #601 - virtual machine guest values go away after a validation error

Updated code to be more ruby 1.87- friendly, refs #427

fixes #427 - Ability to provision xen/kvm guests

this patch adds support to libvirt based hypervisors