conversion_chain_impl
=====================

Applies a series of conversions to get from A to B.  The conversion will be
constructed by a series of mystical incantations unless the "manual" bit is
set.  The algorithm approximates finding the shortest route through the
conversion tree, treating the "weight" of a conversion as the length of the
edge between the nodes.  But if two routes round (down) to the same integer
distance, then the lexicographically first in terms of conversion age will
be chosen.  *This is an algorithm problem (not a variable type problem) that
should be fixed (Dijkstra's algorithm should suffice)*.

set_manual
==========

	some_cc set_manual 1

Indicate that automatic selection of chain links should not occur.

	some_cc set_manual 0

Indicate that automatic selection of chain links should occur.

add_link_back
=============

	some_cc add_link_back a_conversion

Add `a_conversion` to the end of the `some_cc` chain, changing the target of 
`some_cc`.  If `some_cc` was previously empty, the source will also change.

add_link_front
==============

	some_cc add_link_front a_conversion

Add `a_conversion` to the start of the `some_cc` chain, changing the source of 
`some_cc`.  If `some_cc` was previously empty, the target will also change.