Improve how we define and load clinical codes and codelists

[milanwiedemann]

we're defining codes in different ways at different places, e.g.:

• pharmacy-first/analysis/codelists.py

  Lines 59 to 70 in d23e050

  	pharmacy_first_med_codelist = (
  	acute_otitis_media_tx_cod
  	+ impetigo_treatment_tx_cod
  	+ infected_insect_bites_tx_cod
  	+ shingles_treatment_tx_cod
  	+ sinusitis_tx_cod
  	+ sore_throat_tx_cod
  	+ urinary_tract_infection_tx_cod
  	)
  	# Community Pharmacist Consultation Service for minor illness - 1577041000000109
  	# Pharmacy First service - 983341000000102
  	pharmacy_first_consultation_codelist = ["1577041000000109", "983341000000102"]

• pharmacy-first/analysis/pf_dataset.py

  Lines 5 to 15 in d23e050

  	pharmacy_first_event_codes = {
  	# # Community Pharmacy (CP) Blood Pressure (BP) Check Service (procedure)
  	# "blood_pressure_service": ["1659111000000107"],
  	# # Community Pharmacy (CP) Contraception Service (procedure)
  	# "contraception_service": ["1659121000000101"],
  	# Community Pharmacist (CP) Consultation Service for minor illness (procedure)
  	"consultation_service": ["1577041000000109"],
  	# Pharmacy First service (qualifier value)
  	"pharmacy_first_service": ["983341000000102"],
  	"combined_pf_service": ["1577041000000109", "983341000000102"],
  	}