Correcting the biomass objective function

To get feasible results from a model simulation, the biomass objective function (BOF) should add up to 1 mmol/gDW/h. However, this is often not the case, e.g. the BOF of CarveMe does not add up to 1 mmol/gDW/h directly after the draft reconstruction.

Therefore, this needs to be corrected.

The module biomass provides the function check_normalise_biomass() to check if the BOF of a model is consistent and if necessary adjusts/normalises the BOF to add up to 1 mmol/gDW/h.