Better non-standard shell integration support

Better non-standard shell integration support

Added python-shell-prompt-output-regexp to match the prompts
added before output in shells like iPython. With the value of
this variable the output generated for
python-shell-send-string-no-ouput is cleaned up.

Moved completion variables and bindings setup for shell to
inferior-python-mode definition.

Renamed python-shell-completion-strings-code to
python-shell-completion-string-code.

improved python-shell-completion--get-completions string
splitting.

Cleaned up some unecessary messages.

Better code sending need test for python-shell-completion-setup
python-ffap-setup and python-eldoc-setup.

Added example for iPython integration in the commentary section.