24: Celery: Config celery and create periodic task to update firms data

[pedrodef]

• Add the new package 'utils' in app
• Add module csv_to_geojson into the 'utils' package; based from: https://github.com/miquel-vv/csv-to-geojson
• Create 'update_firms_modis' and 'update_firms_viirs' tasks
• Install django-celery-beat, added in the pip requirements files
• Modify the fabric script to run celery beat to use the custom
  • scheduler classes of the 'django_celery_beat' app
• Include environment configurations to set the intervals to be
  • updated each external datasource
• Add a django management command: 'configexternaldatasources' to
  • setup all periodic tasks using the environment settings
• Modify save method of layer's model to support csv files as source files