added factory method CannotBeTheTarget so that card scripts do not need to deal with CannotBeTheTarget0 and CannotBeTheTarget1 directly
compare source if activation is equal, fixes bug where only one activation can
be activated if there are multiple sources

fixes issue 379
replace MagicEntersDrawCardTrigger with Draw factory in MagicWhenComesIntoPlayTrigger
added evoke to ability in card script
replace 'enters draw card' with 'enters draw card <n>'
added Mulldrifter