Blender Git Loki

Armature: remove merge function, use dissolve instead

This was crashing, when looking into a fix I noticed that it gave
hap-hazard results dissolving past forks in the parent/child hierarchy
arbitrarily following one chain.

This functionality is almost identical to "dissolve" which delimits
forks in the chain predictably.

So remove this in favor of dissolve (available from the delete menu).