The condition is checked before executing the action in its sequence, i.e.
effects applied by actions occurring before this in the sequence will be
taken into account by the condition, in contrast with precondition.
The precondition is checked before any action in the group is executed.
In other words, the precondition will act on the state of the game,
ignoring any changes that happen as a result of actions executed before
this one, that are triggered by the same event.
Copies the Action with the added condition that the piece type is type.
Used internally when building variants, to enable convenience actions on
piece type definitions.