Added handling of occupancy cases as lists of occupancy types

Aggregated exposure models usually come defined for certain broad occupancy cases, such as residential, commercial and industrial. The OBM buildings get classified into occupancy types as per the GEM Building Taxonomy v3.0. Several of these types correspond to each of the cases. This MR changes the querying of the OBM buildings so that the list of all occupancy types associated with an occupancy case is used, as it was decided that the occupancy case will not be stored in the OBM buildings table, because it depends on the aggregated exposure model, which is not a part of OBM.

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