Dugi/addon reviews

This adds a system to allow players to find add-ons they seek more easily.

It allows the players to review the add-ons or give them numerical rating (0-10). The reviews can be 'liked' and those liked by the most people are shown the first. A numerical rating based on the frequency of downloads, users' ratings and time players spent playing it is shown instead of the downloads count on the list of add-ons and it is sorted by this number.