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