Add 'humans' app (previously called ship_pirates)

[txels]

Main changes include:

• Copy contents of previously independent app ship_pirates, renamed to humans.
• Settings changes:
  • Add settings that were not on version control (only at the production server).
  • Make secrets into environment variables
  • Split settings into 3 files for clarity: django standard, those from 3rd party apps, and those specific to our project
• Update of some dependencies that didn't work with the (newer) version of django we use