Papercut definition updated

[Alberto Salvia Novella]

While setting importances for around 200 bugs, I realized the papercut 
definition was too complicated to be taken into practice by anyone, 
including myself. So I've overly simplified it.

A papercut is a software defect that is:
- insignificant.
- fixable by one person within a day.
- affecting the future release.

What is to say, if you see something ridiculous affecting Trusty, please 
mark it as affecting "One Hundred Papercuts".

Regards <コ:彡