Create the instance-types api for gcp:

url example:

• http://127.0.0.1:8000/api/cost-management/v1/reports/gcp/instance-types/
  • reporting_gcp_compute_summary

Lets start with the basic compute summary api with the provider_map & serializer combo. 
New files at:

• /koku/api/report/gcp/
  • _init_.py
  • provider_map.py
  • query_handler.py
  • serializers.py
  • view.py

At this point it would probably be best to just get this up in a pr and accepted, then create another issue to cover the group by options and how they map to the materialized views.