Rework spatial data tables

[rbroth]

We want to import administrative regions of different levels for the same country (e.g.: Regions (level 1) and districts (level 2) for Malawi).

At the moment we have several different tables for storing spatial data related to country and admin region location data. We have a country table as well as region and subregion tables, all of which store geographic data that is very similar, but at different scales. We should rework these tables so that thye can deal with multiple levels of administrative boundaries

[rbroth]

Semi-related: for importing spatial boundaries, for the MVP, use GADM data imported with ogr2ogr, then replace with "proper" spatial data later in the project

[rbroth]

todo list for myself

• subregion table has ben reworked to be hierarchical and accept arbitrary regions
• need to rename subregions table
• need to see if "country" table can be removed and subregion/agg_area table be used instead
• check what other geometries are currently imported and if it's in line with what we want the agg_area table to be