Added radioactive skill

This implementation of radioactive splits one-sided dice into a one-sider and a zero-sider. However, it is trivial to change this back to splitting into two one-siders if this is decided.

There is currently no game-level or interface-level test for radioactive, and this might be a *good thing* to have.  ;)

Also, I'd appreciate feedback on the action logging that I've included for attacker die splitting.

http://jenkins.buttonweavers.com:8080/job/buttonmen-blackshadowshade/491/
(and I'll fix the PMD warnings once I work out how to do so)
re "Note, this is a change from the previous behavior of splitting on any attack" --- don't assume all players are familiar with the DHS rules.  Put a comment like this in parens, and also specify what you mean by "the previous behavior", e.g. "the DHS buttonmen site behavior" (or whatever we officially call the DHS site), so people can tell at a glance whether they care about it or not.