[GameAlgebra]: Inserting and deleting moves

[tturocy]

This pertains to the existence of the operations

• insert_move
• insert_infoset
• delete_parent

These operations come directly from the early-1990s Gambit GUI (and continue to be supported). These operations make a kind of sense when we are thinking about drawing a game by hand, as has traditionally been done in the GUi.

However, we are now thinking of a "node" as a history - that is a node is equated with the history of actions leading up to it. To the extent that at the moment a "node" remains linked to a specific C++ object in memory, this creates some interpretation problems - the same physical object in memory now has a different interpretation in terms of the actions that lead up to it.