gui: add qemu/PCIEdit

gui: add qemu/PCIEdit

this patch adds the PCIEdit window and InputPanel uses PCISelector
and MDevSelector

when we detect an iommugroup of -1, we put a warning on top to inform
the user that IOMMU is not activated (but let him add the devices
regardless, so that he can use it after IOMMU is activated)

also puts a warning if he selects a device that shares an iommugroup
with a different device (but not the same device with different
function). that detection is not perfect, but we cannot do really
better

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>