Recurring Nightmare should not be able to return creature sacrificed as cost

[melvinzhang]

reported by sponeta at http://www.slightlymagic.net/forum/viewtopic.php?f=82&t=17929#p190028

test case: TestRecurringNightmare.java

bug is due to different order of actions of Magarena vs MTG. In Magarena, we pay costs first, then choose target. In MTG, choose target occurs before paying costs.

[melvinzhang]

originally reported in https://github.com/magarena/magarena-old-issues/blob/c7ce3b596b3ee06676cca3669ee91331a3f7cd4d/open/issue-211.json

[melvinzhang]

The main difficulty with changing the order is that some effects depends on the cost when they go on the stack, eg {X}: Deal X damage to target creature.

The value X is stored in the MagicCardOnStack that is put on the stack, if the costs are paid after the effect goes on the stack, we will need a new way to update the stack with the value of X. Methods that require a payedCost to return an event would have to be modified.

[melvinzhang]

Alternatively we just fix only Recurring Nightmare by using groovy code to prevent it from selecting the sacrificed creature as a target of its effect.