histedit: delete all non-actionclass related code Now that all actions have been migrated to the class format, we can delete all the unnecessary code that supported the old function format.

histedit: improve roll action integration with fold Previously the fold action would inspect it's class to figure out if it was a rollup or not. This was hacky. Now that finishfold is inside the fold class, let's modify it to check a function (which roll can override) to determine if it should be prompting for a commit message.

histedit: move finishfold into fold class Let's move the finishfold function into the fold class so we can modify it from the roll class more easily.