Fire skill

This pull request enables the fire skill to be used, fixing #258.

Currently, there are a number of outstanding issues:
- the error message on an illegal firing action is 'null'
- there is no logging of a firing action
- the guidance text on the fire page about how much to turn down the fire dice is not strictly correct for a power attack, since it is theoretically possible to increase an attacking die to any value between the target die value and the maximum value of the attacking die

I anticipate that this pull request will evolve over the next week or so with changes that are needed to get Fire working correctly.

There are any number of unaesthetic hacks in the code that I used to get it working. Feel free to criticise these openly if they offend you.  :)

http://jenkins.buttonweavers.com:8080/job/buttonmen-blackshadowshade/307/