#24 Cast runes against attacking alien

[vanitas]

When you afk train or exp, sometimes you may experiance
problems with:
a) lured monsters (e.g. dwarf guard when you are
cavebotting in the dwarven mines)
b) other players which attack you
Goal of this FR is to add an option to automatically
cast runes (sd/hmm/explo/gfb) against such creatures so
that they get killed fast and efficently.