Add ability to add/remove DNS records when adding/removing a host entry.

A host in DNS must have an IP address so a valid IP address is required
when adding a host. The --force flag will be needed too since you are
adding a host that isn't in DNS.

For IPv4 it will create an A and a PTR DNS record.

IPv6 isn't quite supported yet. Some basic work in the DNS installer
is needed to get this working. Once the get_reverse_zone() returns the
right value then this should start working and create an AAAA record and
the appropriate reverse entry.

When deleting a host with the --updatedns flag it will try to remove all
records it can find in the zone for this host.

ticket 238

ipalib/util.py

@@ -170,3 +170,18 @@ def isvalid_base64(data):
         return False
     else:
         return True
+
+def validate_ipaddr(ipaddr):
+    """
+    Check to see if the given IP address is a valid IPv4 or IPv6 address.
+
+    Returns True or False
+    """
+    try:
+        socket.inet_pton(socket.AF_INET, ipaddr)
+    except socket.error:
+        try:
+            socket.inet_pton(socket.AF_INET6, ipaddr)
+        except socket.error:
+            return False
+    return True