Updated OneJointIK with Fixed Version

I've updated the OneJointIK node to a version that actually works.

Somehow, in the more than a year the old version has been up, no one told me it was horribly broken.

The new version no longer randomly borks itself due to a floating point error in the clamp function. It now supports Bone2Ds, as it was always meant to. It now supports horizontal flipping of the rigged 2D model, as long as the model's root node is assigned correctly. It now throws fewer and more informative errors in some situations.

If you are one of the people who tried to use this node and found it broken, I am sorry. I meant for this to be a general solution anyone could drop into their project without fuss.