Partial migration to the new Decision framework.

test-single-encounter.rb is the only way to run a test right now.
File structure, state rework, started WeightAI

* Created a subfolder layer and reorganized the files.  Not sure if I'm
100% happy with this.
* Current phase logic is now in the Player class (in the new
player_state.rb file).
* WeightAI now (sort-of) works, it does a depth-first sim of the
remainder of the turn for each decision and decides which outcome it
likes the best.
* Weapons/heroes are migrated to the new decision framework.