2.2 Level object documentation

[glistermelon]

If you find it useful, I wrote up a draft of level-object.md with most 2.2 triggers/other stuff accounted for here.

No pull request because its a rough draft and I'm not motivated to finish it currently, but if I do finish it I'll submit a pull request instead.

Personally, though, there are so many different object properties in 2.2 that it might be more helpful for readers if most of them were categorized / split into different tables based on the triggers/objects that actually use each property.

[glistermelon]

Also, here's a draw-up for properties 276 (yellow), 283 (green), and I believe that black is 262 (if that's the case I may need to swap 0 & 1 for 1 & 2).

And, 274 is a bool that indicates whether an object is/has the "Group Parent ID".

[glistermelon]

Currently unidentified properties 155 and 156 are also mentioned here on line 5029.