Core driver implementation with ebtables support

This patch implements the core driver and provides
- management functionality for managing the filter XMLs
- compiling the internal filter representation into ebtables rules
- applying ebtables rules on a network (tap,macvtap) interface
- tearing down ebtables rules that were applied on behalf of an
interface
- updating of filters while VMs are running and causing the firewalls to
be rebuilt
- other bits and pieces

Signed-off-by: Stefan Berger <stefanb@us.ibm.com>

generator.py

@@ -175,6 +175,7 @@ skipped_types = {
      'virConnectDomainEventIOErrorCallback': "No function types in python",
      'virConnectDomainEventGraphicsCallback': "No function types in python",
      'virEventAddHandleFunc': "No function types in python",
+     'virNWFilterPtr': "No function types in python",
 }
 
 #######################################################################
@@ -273,6 +274,7 @@ skip_impl = (
     'virConnectListStorageVols',
     'virConnectListDefinedStorageVols',
     'virConnectListDefinedInterfaces',
+    'virConnectListNWFilters',
     'virConnGetLastError',
     'virGetLastError',
     'virDomainGetInfo',