Fix: SkillTree Ratio

* SkillTree canvas size from 500x500 to 597x500, this is to match the
ratio on the Path of Exile website (916x767)
* The multiplier used for mapping between canvas and data is now
calculated using width and height. Before it only used the height of the
canvas, which worked fine as long as the width and height where the
same.
* The images from the path of exile site are now bigger, so less scaling
is needed.