Weak and mighty die skills

Fixes #279. Fixes #277. Fixes #1050.

This pull request achieves the following:
- implements the weak die skill
- implements the mighty die skill
- changes the behaviour of berserk so that the attacker does not lose the swing/option die character

Known issues:
- logging does not explicitly say that a die "shrinks" or "grows", only that the recipe changes
- logging of recipe change when a weak/mighty die is targeted by a trip attack is in an order that does not truly reflect what actually happens,

e.g.,
"test2 performed Trip attack using [t(4):4] against [wHo(16):5]; Attacker t(4) rerolled 4 => 3; Defender wHo(16) rerolled 5 => 5, recipe changed from wHo(16) to wHo(20), was not captured"

although the change in recipe occurs BEFORE the trip roll of the targeted die

- does not definitively address #647; the current implementation is Weak then Mighty, but this may change in the future according to what is decided (although the skill combination Weak Mighty does not currently exist on any button recipe)

I propose that the known issues be addressed in separate issues as necessary.

http://jenkins.buttonweavers.com:8080/job/buttonmen-blackshadowshade/454/