Find'n'Link bones automatically

[igelbox]

Approaches (off the top of my head):

1. Naive minimum distance between source/target bone origins.
   May link sibling bone to a parent in case if there's many small bones in a region, e.g.:

chest        -> neck
|- neck      -> |- head
 \ clavicle  ->  \ clavicle

Which result in implicit applying neck animation to clavicle while would look weird.

2. Take hierarchy into account, e.g.:

• Condense the armature graph
• Find most relevant source-to-target nodes condensed graphs
• Link most relevant source-to-target bones examining paths (each node has just one child) between respective condensed nodes