topic.update(): create this new method
topic.update(): create this new method

The API allow a user to update a topic, but the python library wasn't
providing the method to do it.

Now a user can call topic.update() to update topic informations.

Change-Id: I381996f95a2d44db488a85f08b03312e60089e9d

redhat-cip/python-dciclient,redhat-cip/python-dciclient