Add a Changelogs Screen

[Willard21]

I want a screen that shows all the recent changes, along with dates, version numbers, and contributor names. Ideally it should pop up automatically for returning players that haven't seen the pop-up yet. New players don't need to see the changelog, so no popup for them. This can be accomplished by storing the last known version in the player's IDB settings, and displaying the popup if the game's version exceeds the last known version.