Decorators implemented in a much more simple and generic
way than before, we can use them in other place too.
3 deco implemented:
@on_signal(emission, source)
@message_handler
@on_text_change
I choosed the 'strange' on_* naming convention to not
clash/confuse with normal callback functions, tell
me if you don't like.
Davide Andreoli
5913721de9