Add support for 'Armor As Dice' from Pyramid #3/34

[PrinceOfIonia]

Found in Pyramid #3/34 page 32. Basically just use the same formula for the Modifying Dice + Adds rule. Here is the code for how GCS did it in case you want to see how they did it: https://github.com/richardwilkes/rpgtools/blob/master/dice/dice.go#L273-L310

The issue then comes to the damage calculator, it needs to be slightly retuned when this option is enabled. Pyramid #3/34 displays how to do this, but I will give a "nutshell" version of it.

To calculate the damage from a 3d+2 attack versus 10 DR (converted to 2d+3) using the Armor as Dice rule, first subtract the dice. The attack’s 3d minus the DR’s 2d leaves 1d of damage. Next, subtract the adds. The attack’s +2 minus the DR’s +3 results in -1. This leaves the final damage as 1d-1. Roll 1d & subtract 1 from the result to determine the injury.

I realize that having the extra digit space for DR to be listed as dice on the character sheets might not work out, so you can just instead do the conversion on the damage calculator and not have DR listed as dice format on the character sheet. I recommend showing DR converted to dice if you hover over the DR on the hit location however.