Merge pull request #6524 from RosettaCommons/roccomoretti/tweak_ligand_anchor
[Foldit] Add anchor for Tweak Ligand tool
Players have been asking for a way to control which "side" of the ligand changes with the TweakLigand tool.
This PR adds a movable Pin (like the FoldTree pin) which allows them to specify an anchor atom. The anchor atom is held fixed, and everything else rotates from it. (Technically, the ligand is rotated, and then the position and orientation of the anchor atom is adjusted to match.)
This involved abstracting and generalizing the PinGeom from the FoldTreeComposite.
I also adjusted how the rotation amounts were processed, to allow for slightly smoother click-and-hold behavior.