Adds choropleth legend
Merge branch 'develop' of github.com:CartoDB/cartodb20 into develop

* 'develop' of github.com:CartoDB/cartodb20:
  Update NEWS.md with a heads up to run the task to create the cdb_importer schema
  Include importer schema creation task in UPGRADE notes
  [importer] Reflect state changes in DataImport as communicated by the importer
  [importer] Check available quota before loading data