enable boundary conditions from init sim

lets the glacialcycle simulation containing H use lateral H-boundary conditions which use the initial result as a basis and add the glacial pressure. For that to work, we require model_props.py to have the path to the initial result, so that it can be read in the python files from glaciationBCs. It didn't work out to put it inside serial_model_from_serial and serial_model_from_parallel because the wildcards of the output weren't the same and not adding it to the output would lead to skipping the rule on repeated simulations. Thus the easiest working solution for me was to add the corresponding line the the model_properties.py immediately before the glacialcycle simulation rule. See https://github.com/cbsilver/glaciationBCs/pull/2