Remove getters/setters in `GenericClient`, either use @property if they are required or remove them

[aurelg]

I noticed several getters/setters in GenericClient. The implementations of the corresponding attributes is quite simple, and their (unlikely) changes would only impact feedspora itself and would be easy to manage without side effects. I think having direct read/write access to attributes would be enough and simplify the code.

OTOH, if there's a good reason I don't get yet to have getters and setters, they should probably be implemented with the @property (see here) to prevent direct access to attributes (and allow for more readable code when calling them).

[wilddeej]

I don't know of any compelling reason why these need to stay, actually. I wonder if there would be any pylint impact, however - I see many complaints in the test code about accessing internal variables...