For convenience, add ex_create_port_forwarding_rule and
ex_delete_port_forwarding_rule method to the CloudStackNode class.

For consistency, also rename "ex_add_ip_forwarding_rule" to
"ex_create_ip_forwarding_rule".

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
To make it more clear, use keyword arguments.
Update CHANGES.