Add CustomValueDecoder for new spells options

BuffSpell now has it's "value" param stored as string. It's being
 evaulated by CustomValueDecoder before calling unit's applyBuff()

CreateUnitSpell's "count" param is now string. It's being evaualted
 before launching cycle - this allows spells such as "Tosters!!!"

Add TriggeringCondition new event "BeforeCreate" so that "Warlord"'s
 buff calculates correclty, excluding self. That condition is being
 passed to unit before he get's placed on board.
Add "ModQuality" buff

- ModQuality buff gets erased on each recalculateFieldModifiers() tick
- ModQuality turns on special qualities on units modQualities int
- Units hasQuality() method checks both integers - qualities and
  modQualities