Introduce Effects for Spell, test behavior on generated HolyNova,
HolySmite and FireBall.

I am not completely satisfied with the JSON pattern describing effects.
It reads:
  "effect": {"target": {"select": "any"}, "damage":6}
  
Where I would have prefered:
  "effect": {"damage": {"target": {"select": "any"}, "amount": 6} }
  
I am not completely sure that they are equivalent in terms of
expressivity. The second pattern just seems more elegant to me. But as
the generator was more straightforward to implement for the first
pattern, I sticked with it.
Merge remote-tracking branch 'origin/master'

Conflicts:
	hearthstone/src/com/hearthstone/Player.java