[python] filter returns an iterator in python3, make sure it stays a list
[python] cleanly shutdown messages_app
[python] more cleanup

- pep8: 4spaces indentation
- print_funtion
- use 'in' instead of has_key for dicts
- log stuff not tested...
[python] fix realtimeplotapp

realtimeplotapp calls Stop() on IvyMessagesInterface and expects it to only unbind.
Add an extra Shudown method for messagesapp that also stops Ivy.