Rename with_recall to by_last_action and clarify meaning of "last action" #1143

The H-selector operation currently labeled with_recall could be misunderstood to imply perfect recall for the named player throughout the game. That isn't the intention of the operation - it's documented clearly to be "recalling the player's last action played", which is valid even in the case of (earlier) imperfect recall for the player. But it would be an easy thing to confuse. Therefore, we want to rename this to by_last_action.

Meanwhile, the implementation of with_recall groups by action label only. An action properly is an (information set, label) pair; by_last_action needs also to key on the information set. This is the usual case and is in fact required in order to ensure this can be used to easily maintain perfect recall by construction.