Implemented config parameter to turn on alternative effect value roll distribution

[FominArtmind]

Motivation: current effect value distribution is linear, that is, you have equal chances to get min, max or any other value inside the range of the effect. It's good to have the possibility to turn on alternative distribution where min and especially max values are less likely to be rolled. Such distribution allows to increase available effect range without affecting the balance much, that is, getting the same average value as with linear distribution. That encourages the player to hunt for items with high values more and reroll (augment) the effect more times to gain that high value that is not easy to roll.

Not obligatory text describing one concept. :)
Additional positive effect is the possibility to create "meaningful magic items" and similar things. That is, imagine that effect property on magic item has range 10-110 while on rare item it has range 40-80. With linear distribution magic/rare average values are the same - 60 and magic one is more preferable since it's not difficult to roll value above 80 (max rare value) on it. With the proposed distribution average value for magic is around 40 while for rare it's around 52. Getting the value above 70 for magic item will have only 16% chance (with only 1% for values in highest range 100-110) in comparison with 40% in linear distribution case. Taking into account that you have only 20% to get two effects on magic item while on rare you get them always, two facts can be valid the same time:

• on average rare item is much better that magic one
• you have a very small chance that very good magic item will be better than any rare item possible (for example, if you need max dps, that is, dmg + attack speed effect combination)

This makes magic items not just something that you use early game and then trash always but something that you can have particular case of usage even in the late game if you know what you are seeking for, making overall loot system less plain.

Backward compatibility: full