Feature: Enable history traversal

[Tohaker]

The existing data structure for a channel contains a history array, with all the previous map UUIDs.
These UUIDs are sorted latest to the earliest, meaning the ID at index 0 is the most recent, and the ID at index n was created the longest time ago.
It should be possible for a user to not only recall the entire history but also reset the game state back by x number of turns.

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Command ideas:

• /map history returns all maps in the history array, in their existing order. Each map should be numbered.
• /map history turns:5 returns the last 5 maps in the array. If fewer maps exist, just return those.
• /map history rewind:3 "rewinds" the game by 3 turns permanently overwriting the game. If possible, a warning before this is executed should be provided.