hinge, Autoclose remix

Remix of airald's excellent autoclose hinge.

I have changed a couple of things to suit my needs.

1. The autoclose angle has been halved. Mainly to reduce the height rise of the door.
2. I have added an option for a pan-head bolt (M4)
3. I have added a back plate to reduce the stress on the acrylic door I plan to use.
4. I have added left and right handed versions. The left hand version is designed to mount on the left side of a door (with it opening towards you).