Calculating skilling probabilities

[data-dependent]

When skilling outside of a guild, the probability of success is determined by two variables: low and high. The probability then is (N+1)/(255+1), where N=low*(99-lvl)/98+high*(lvl-1)/98 and each division is integer division and so rounds down. This has been shown experimentally by the wiki team and confirmed by jmods. Note, the term for inside of guilds is N=(low*(99-lvl)+high*(lvl-1))/98. The effect of probability-altering equipment is to change the N value. For instance, if N is the term for the success probability of harpoon fishing with a normal harpoon, then floor(1.35*N) is the corresponding value for a crystal harpoon, which has a 35% boost.

This is different from what is currently in the code and disagrees with assumption 4. (Love the project, by the way!)