Adjust occupancy sub-types classification and narrow down commercial building classes based on occupancy type

This merge request addresses these two issues:

1. Narrowing down commercial building classes based on occupancy type: The GDE prototype code assigns SERA building classes and their probabilities to each OBM building, based on its location. The previous version of the code only narrows down the possible building classes as a function of the number of storeys, when the latter is available in OSM/OBM. This new feature allows for further narrowing down of the commercial building classes using the OCCUPANCY_TYPE field of the SERA CSV files. If the occupancy type of the building is sufficiently constrained in OBM, then we can only assign, for example, "Trade" building classes to OBM buildings labelled as COM1, and so on.

2. Adjusting occupancy sub-types considered from OBM to reflect sub-types considered in ESRM20: ESRM20's exposure model comprises the following occupancies categories and their subtypes:

• Residential:
  • residential buildings considered in national censuses and statistics (they usually include mixed commercial and residential use)
• Commercial:
  • offices
  • wholesale and retail trade
  • hotels and restaurants
• Industrial:
  • manufacturing
  • mining
  • quarrying
  • construction