[Node Constraints] Additional features & bug fixes

[Coppersocket]

There's two key features of Node Constraints that is sadly lacking that would be very beneficial, and useful to have.

First off is the ability to mirror the movement of the parent bone. By this, I mean for example that if you were to move the parent up, the child would move down instead, or if it's already in a position where it'll opposite, it'd move with the parent and move up.

Second would be to force the child to stay in it's current location, but instead of moving it's coordinate it will always turn to face the coordinate of the parent. So, the Child's rotation is bound by the Parent's position rather than the Parent's rotation.

Third, bug fix: Under certain parenting conditions (Very common ones), the game will stop remembering which state the bone was in originally, and will transpose a new value to the child bone as the default. This means that you no longer can default the bone back to the original value of the item or character. This is a pretty large issue, if it manages to happen it can literally break a scene if you do not keep the values in mind yourself.

(The next might be a KKPE issue) There's also the issue of that when a bone is already parented and you go into KKPE Advanced to adjust the parented bone, instead of making any changes you've made into temporary changes it makes them permanent. This only happens while the bone is affected by Node Constraints.

[ManlyMarco]

Can you split out the things not addressed by the PR above into a new issue(s)?