Merge motion.py and engine.py

[ttan]

It would be nice to have just one file that manages everything.
My initial idea was to make a unique web service that can be triggered by Motion and handle Telegram message; this last point though was hard because, in order to receive messages, the process hangs on the bot polling and can't manage a web service at the same time in one process.
Things got complicated so I opted for this current structure.