The fermentation host library, as the bioreactor parameter panel needs it: organism key -> the value every host_* field falls back to when left blank.

The panel used to print "library value" in each of those boxes, which told the user that a number existed but not what it was, so overriding one meant guessing first. Serving the library from the same module the simulation resolves hosts through is what keeps the printed number and the simulated number the same one.