Added TileExposure and ExportHandler classes

config_example.yml

gdeexporter/configuration.py

gdeexporter/database_queries.py

gdeexporter/gdeexporter.py

gdeexporter/handler.py

gdeexporter/tileexposure.py

tests/data/config_for_testing_cost_case_invalid.yml

tests/data/config_for_testing_geographic_bbox.yml

tests/data/config_for_testing_geographic_bbox_missing.yml

tests/data/config_for_testing_geographic_data_units.yml

...data/config_for_testing_geographic_data_units_missing.yml

tests/data/config_for_testing_geographic_quadkeys.yml

...s/data/config_for_testing_geographic_quadkeys_missing.yml

tests/data/config_for_testing_good.yml

tests/data/config_for_testing_good_people_case_invalid.yml

tests/data/config_for_testing_missing.yml

tests/data/expected_results_append_OBM_buildings.csv

tests/data/expected_results_append_lumped_buildings.csv

tests/data/test_database_set_up.sql

tests/test_configuration.py