Feature: define geographic area to run
This MR includes all features needed for the user to specify the geographic area to run (i.e. whose output will be produced) and the interpretation of those geographic areas as lists of quadkeys to be processed. This is all handled by the Configuration
class.
The geographic area can be specified as a list of exposure entities (e.g. countries), data units (e.g. administrative units), quadkeys or a bounding box.
\fyi @fd