Build the carrier list using all slots. Closes #328.
Build the carrier list using all slots. Closes #328.

A recent ETsource change introduced converters whose input is a carrier
not seen elsewhere in the graph -- e.g. imported_steam_hot_water  --
which the converter changes into a different output carrier. As the
Engine builds its list of carriers using *outputs* only, and these
"orphan" input carrier are never used as output, they would not be
correctly set up in Etsource::Topology#import.

Qernel::Graph#carriers has been changed to scan all converter slots
when creating the list of carriers. This results in the "orphan" input
carriers being correctly configured.

quintel/etengine,quintel/etengine,quintel/etengine,quintel/etengine