Feedback system overhaul

We have learned that creating a functioning marketplace is a very difficult problem. Now we have tried to improve the marketplace by creating an overhaul to the feedback system.

In the new system, feedback is always enabled when an request is finished in a way or another. However, localbitcoins.com system tries to determine "confirmed" status for feedbacks with an algorithm. A confirmed status means that we have strong confidence that the feedback is legit.

Also users can block other users with the feedback mechanism. This helps stopping escrow spammers or buyers, who try to hedge bitcoin price using the system.

Our next goal is trying to limit the advertisement spam in the system. Also fine-tuning the processes more fluid.