Fix a few bugs about io

[Hydrop002]

• When importing a bedrock model, if there are both locators with rotation and without rotation in the same group, those locators without rotation may incorrectly get rotated.
  e.g.

{
	"name": "bone",
	"pivot": [0, 0, 0],
	"locators": {
		"locator": {
			"offset": [0, 0, 0],
			"rotation": [-20, -35, 60]
		},
		"locator2": [0, 0, 0]
	}
}

• Parsing of modded_entity always encounter problems, such as bone rotation problem caused by addChild out of order. So I improved it a little bit. I haven't considered model formats for versions of 1.17+ because I haven't read the code for those versions yet.

[JannisX11]

The locator issue is a good catch 👍
Will look at the modded entity import code another time. This feature is no longer supported for more recent versions, so it is more or less deprecated.