Improve api.conf usage

[hezanathos]

Change CBWApi behaviour so that it accepts any prototype :
CBWApi(*args, **kwargs)

Handle the retrocompatibility, no change to previous usage can happen.

Then handle a new named parameter for this constructor, that allows providing an api.conf path and loading it.
Once its done, change all examples to use this and ad a top comment(for each example) to ask the user to change the path parameter if required.