Abiotic simple - conservation of energy with bounds setting

At the moment, the `abiotic_simple` model sets values that fall outside the range of expected values to the upper or lower bound value. This is true for all updated variables; the bounds are defined in the `abiotic_simple/constants.py`. The problem is that this approach does not conserve energy or matter.

I currently do not have a solution ready. For now, we should produce a warning or error message.