Global DNS options

Implement API for DNS global options supported in bind-dyndb-ldap.
Currently, global DNS option overrides any relevant option in
named.conf. Thus they are not filled by default they are left as
a possibility for a user.

Bool encoding had to be fixed so that Bool LDAP attribute can also
be deleted and not just set to True or False.

https://fedorahosted.org/freeipa/ticket/2216

install/updates/40-dns.update

@@ -20,3 +20,6 @@ add: basedn: 'cn=privileges,cn=pbac,$SUFFIX'
 add: filter: (objectclass=*)
 add: ttl: 10
 
+# add idnsConfigObject if it is not there already
+dn: cn=dns, $SUFFIX
+addifexist: objectClass: idnsConfigObject