Complete missing documentation

[dt-woods]

There's quite the laundry list of missing module and method doc strings.

	Module	Method name
0	__init__.py	write_distribution_dict
1		get_distribution_mix_df
2		write_distribution_mix_to_dict
3		get_consumption_mix_df
4		write_consumption_mix_to_dict
5	aggregation_selector.py	subregion_col
6	ampd_plant_emissions.py
7	coal_upstream.py	eia_7a_download
8		read_eia923_fuel_receipts
9		_coal_code
10		_transport_code
11		generate_upstream_coal_map
12		wtd_mean
13	combinator.py
14	consumption_mix.py	surplus_pool_dictionary
15		consumption_mix_dictionary
16		check_trading_normalized
17	distribution.py	distribution_mix_dictionary
18	dqi.py	lookup_score_with_bound_key
19	egrid_emissions_and_waste_by_facility.py
20	egrid_energy.py	list_egrid_facilities_in_efficiency_range
21	egrid_flowbyfacilty.py
22	egrid_FRS_matches.py
23	eia_trans_dist_grid_loss.py
24	eia860_facilities.py	load_eia860_excel
25		eia860_balancing_authority
26		eia860_primary_capacity
27		eia860_EnviroAssoc_so2
28		eia860_boiler_info_design
29		eia860_EnviroAssoc_nox
30		eia860_generator_info
31	eia923_generation.py	load_eia923_excel
32		group_fuel_categories
33		calculate_plant_efficiency
34		efficiency_filter
35		eia923_generation_and_fuel
36		eia923_boiler_fuel
37		eia923_sched8_aec
38	elementaryflows.py	map_emissions_to_fedelemflows
39		map_compartment_to_flow_type
40		add_flow_direction
41	emissions_other_sources.py
42	generation.py	eia_facility_fuel_region
43		add_flow_representativeness_data_quality_scores
44		add_temporal_correlation_score
45		wtd_mean
46		geometric_mean
47		calc_geom_std
48	generation_mix.py	olcaschema_genmix
49		olcaschema_usaverage
50		olcaschema_international
51	geothermal.py
52	globals.py	list_model_names_in_config
53	hydro_upstream.py
54	import_impacts.py
55	main.py
56	manual_edits.py	reassign
57		remove
58		check_for_edits
59	model_config.py
60	natural_gas_upstream.py
61	nuclear_upstream.py
62	olca_jsonld_writer.py
63	petroleum_upstream.py	generate_petroleum_upstream
64	PhysicalQuantities.py	N/A (methods by others)
65	plant_water_use.py
66	power_plant_construction.py
67	process_dictionary_writer.py	process_metadata
68		lookup_location_uuid
69		exchange
70		exchange_table_creation_ref
71		exchange_table_creation_ref_cons
72		gen_process_ref
73		con_process_ref
74		exchange_table_creation_input_genmix
75		exchange_table_creation_input_usaverage
76		exchange_table_creation_input_international_mix
77		exchange_table_creation_input_con_mix
78		process_table_creation_gen
79		location
80		process_description_creation
81		exchangeDqsystem
82		processDqsystem
83		exchange_table_creation_input
84		unit
85		exchange_table_creation_output
86		uncertainty_table_creation
87		flow_table_creation
88		ref_exchange_creator
89		process_table_creation_con_mix
90		process_table_creation_genmix
91		process_table_creation_usaverage
92		process_table_creation_surplus
93		process_table_creation_distribution
94	solar_thermal_upstream.py
95	solar_upstream.py
96	technosphereflows.py	map_heat_inputs_to_fuel_names
97	upstream_dict.py	_unit
98		_process_table_creation_gen
99		_exchange_table_creation_ref
100		_flow_table_creation
101		_exchange_table_creation_output
102	utils.py	find_file_in_folder
103		create_ba_region_map
104		set_dir
105		join_with_underscore
106	wind_upstream.py