LitPop, lines_polys_handler & high-resolution GIS (openstreetmap) data #290

With the lines_polygons branch (on climada_python) and the openstreetmap data_loader (on climada_petals) taking shape, there's a few reflections on the intersection of those two modules, as well as on some aspects where LitPop plays a role:

• LitPop can be used for providing a value estimate of the respective shapes (e.g. buildings, province polygons, ...) - halfway implemented currently, as discussed in the respective thread of the pull request Code Review: Methods to handle lines and polygons with CLIMADA exposures #221

• Vice versa, detailed map knowledge of where high-value or low-value areas are (such as buildings vs. waterbodies, grassland...) could be used to downscale LitPop exposures as so:

   1)  Define Low-Value areas
   2) Re-assign LitPop values only to places outside low-value areas ("Downscaling")
  

cf the working-flow that's still left as a stub on climada_petals > feature/osm_expmaker branch (code-wise not really relevant anymore, methods would have to be re-written anyways, more as a conceptual remainder), visually:

I'll leave it here so we can pick up the discussion on which functionalities & disaggregation methods would be useful to have implemented, in the end.