[virt-tools-list] virt-manager gtk3 and virtinst merge now on master branch

[Cole Robinson]

The virt-manager gtk3.2 branch has now become virt-manager master. Previous
master is now on a 0.9-maint branch, if we ever want to do bug fix releases of
the old 0.9 series.

Since virtinst has been merged with virt-manager, the virtinst master branch
has been emptied except for a simple readme. There's now a 0.6-maint branch
which contains the previous virtinst master.

So the next virt-manager release will definitely be gtk3 based!

Thanks,
Cole