Add support for bridge interface type

- Example for configuration inside Vagrantfile:
  test_vm1.vm.network :public_network, :dev => "br0", :mode => 'bridge',
    :type => "bridge", :model_type => "e1000"
Fix destroy in vagrant 1.5.1+

Addresses issue pradels/vagrant-libvirt#166
load missed module for 9p
Merge pull request #176 from stvleung/master

Fix destroy in vagrant 1.5.1+
Merge pull request #175 from mafigit/add_bridge_interface_support

Add support for bridge interface type
add module 9pnet_virtio
Added cleanup capability for 9p mounts

This will allow proper halting, and reloading
Merge pull request #179 from stvleung/master

Added cleanup capability for 9p shared folders
Replace HandleBoxUrl with HandleBox
Do not use 9p by default
Reenable PrepareNFSSettings, closes #180
Document synced folder types
Vagrant-cachier tested to work
Verify libvirt version before enabling 9p
Merge pull request #181 from sciurus/HackNashville

Fixes for synced folders and HandleBox
Domain type 'kvm' should be configurable and use qemu:/// uri.

Previous versions simply defaulted to 'kvm'. Now that they default to
'qemu', there is typically a 5x performance decrease that makes vagrant
unusably slow.
Merge pull request #182 from purpleidea/kvm-fix

Domain type 'kvm' should be configurable and use qemu:/// uri.