feat(networks): the network pages on Bootstrap's cards, tables and dialogs

As the storage pages; reviewed with Codex.

- The list is a card per network: its name with Active or Stopped and
  Autostart badges, its type (network_mode: Isolated, NAT, Routed,
  Open, Bridge, Macvtap, SR-IOV), its device, and each address with
  its DHCP range; a bridge or macvtap network's addresses come from
  the outside network.
- A network's page: its heading starts or stops it, the menu sets
  autostart and deletes a stopped one. A Network card tells its state,
  type, bridge or interface, MAC and what the type does; a card per
  address (every <ip>, each with its DHCP range dialog, which libvirt
  takes on a stopped network); its fixed addresses of every subnet in
  one table, searched, each with Edit and Delete, one dialog adding
  and editing them; the VMs whose definition names it, connected or
  configured, linked (wvmNetwork.get_vms, one domain listing, a VM
  undefined meanwhile left out); its
  bandwidth limits where libvirt sets them (not on macvtap or SR-IOV
  networks), in KiB/s, from the saved definition with a note that a
  running network takes them when restarted; its XML in an accordion.
  The page reads the running and the saved definition once each, and
  only to render itself: its actions, which all redirect, read nothing
  of it first.
- The New network dialog is one form, as the New pool one: the type
  as radio cards (the radio_card.html include, now shared by both),
  the chosen type's fields only, IPv6 with its box, a bridge or
  interface suggested from the host's (get_host_interfaces, not the
  bridges libvirt made for its own networks); a refused network or
  one libvirt refuses opens the dialog again with what was entered,
  the reasons beside the fields and focus on the first.
- What the New pool and New network dialogs share is one script,
  static/js/choice_dialog.js: the radio cards show their fieldsets
  (data-kinds) and a refused form opens again focused on its first
  refused field; each dialog keeps only its own changes.
- The fixed-address dialogs per family go to the page's own dialog.

networks/tests/test_audit_rows.py

@@ -96,5 +96,5 @@ class NetworkRowTests(TestCase):
                                "dhcp4": "on"})
         self.client.post(url, {"create": "", "name": "bad name!", "forward": "nat"})  # invalid form
         response = self.client.post(url, {"create": "", "name": "lab", "forward": "nat", "subnet": "203.0.113.0/24"})
-        self.assertIn("* This host has a network of that name", [str(m) for m in get_messages(response.wsgi_request)])
+        self.assertContains(response, "This host has a network of that name")  # in the dialog, open again
         self.assertEqual(rows(), [("Network audit-net: add", True), ("Network lab: add: name already in use", False)])