[docs] socketserver documentation

[Lipska TheCat]

Hi

I have recently begun to investigate Python and have come up against a number of 

apparent issues with the documentation

20.19.3. RequestHandler Objects

investigating the socketserver.py code I believe the docs should 
be altered to refer to the class BaseRequestHandler and not RequestHandler.
I also think that some class specific docs for StreamRequestHandler and DatagramRequestHandler
would be useful.

I don't know what system you use to maintain the documentation but I'd be happy to contribute some changes/additions 

Kind Regards

lipska