Custom dragon claws ko chance model

[Sacca-1]

This new model is a big improvement over the standard ko chance model, because the hitsplats from dragon claws land on two ticks, it now:

• Takes into account the different hitsplat patterns (which of the 4 accuracy rolls
  lands).
• Takes into account any HP healed in between the two ticks of damage.
• Combines the chance of dying from the damage of each tick into a single ko chance.

Now also correctly matches hitsplats for the dragon claws - granite maul combo, for which the hitsplats tend to appear as 2x claws -> 1x maul -> 2x claws.