virtinst: add nwfilter support

This allows to make use of libvirt network filtering support with virt-install.
With the additional option "filterref" in the --network parameter one can
configure any defined nwfilter per network interface, i.e.:
virt-install ... --network network=mynet,model=virtio,filterref=clean-traffic

(crobinso: add an xmlparse test case)
uihelpers: Don't list 'lo' as a macvtap interface (bz #980606)
console: Catch spice connection errors (bz #971558)
packageutils: Don't implement our own search dialog (bz #746011)

Our search dialog isn't as full featured as packagekits, so just call
out to that. This was originally avoided because it doesn't full
provide the semantics we want, but it's close enough and saves us
from duplicating all their work.
console: Fix spice with TLS (bz #904295)

We now use the same CA trust store as virt-viewer's default, which is:

~/.spicec/spice_truststore.pem
details: Track serial pages as console tabs

A bit cleaner conceptually, and shrinks the ever growing details.py
manager: Merge some row creation, drop unneeded row keys
preferences: Stats interval can't be less than 1
details: Properly limit machine type list by guests arch/type
details: Fix description field spacing
addhw: Fix FS UI for non-qemu
Replace set_property("visible") with modern set_visible
graphwidgets: Make a division check more robust

Not an issue in practice, but I was stubbing out some parts of the code
in trying to track down a memory leak and this check failed.
manager: Disable graph data func if graph isn't visible

Seems like pygobject is a bit leaky with tree row accesses, and
the cell cb hammers on that quite a bit, even if the graph isn't showing.
manager: Separate stats and state update callbacks

There's no need to be resetting row keys like VM name, state, on every
'resources-sampled' signals, since we have had finer grained status-changed
and config-changed signals for a while. This seems to reduce the memory
leak on F19 as well.
baseclass: Build error object on demand

Should speed things up a tiny bit in the common case
manager: Use consistent row spacing even if we disable all graphs
graphics: Fix default autoport value

default_cb doesn't want yes/no, it wants True/False
addhardware: Modernize 'graphics' UI

- Drop SDL, it doesn't mesh with modern libvirt
- Drop keymap, modern qemu/virt-manager handle this automagically
- Drop big text fields
- Misc other cleanups and simplifications
autodrawer: Drop note about broken child_get_property

I can't reproduce anymore