Add transactional API

[narfman0]

Make API where every action can be a transaction instead of a linear progression on the world. Every transaction (struct?) should have a commit and undo type action, such that the program can be given a set of transactions to rebuild the level in the same way, then a set of transactions to undo to deconstruct the world.

This will both make undo/redo support easy and make autosave/backup feature less resource intense (than saving every few seconds). Low priority given the time effort vs benefit ratio