Feature/fix redis leak windowmanager

The window manager didn't clean up everything when a key was expiring (not ACKed in time). 2 kind of data was pilling up:
1. the list of expired message key
2. the data of each message

Also one modification the general prefix keys in redis has been changed. Now each window manager has the following key: "middlewarewindows:[transport_name]:...." while before it was "middlewarewindows:[transport_name]:[transport_name]:...." .... thinking about it this might need to be changed in order to get more secure naming.