Bond-Centric Dihedral Angle

Hey Everyone,

I’ve added dihedral manipulation to the bond-centric manipulation tool. You
can twist all atoms bonded to one side of the selected bond by left-clicking
and dragging on one of the atoms one bond away from the selected bond, or
change a single atom’s dihedral angle by right-clicking and dragging on it.

There are two special cases that I’ve found where the behavior is a little
odd, I’ve submitted bugs for them as I don’t have the time to fix them at
the moment with everything going on at Uni, hopefully I’ll get around to
fixing them shortly after I’ve finished. However they are quite peculiar
cases and should be quite rarely needed so hopefully it won’t be a major

Let me know what you think, any suggestions, etc!