Create a Settings class for settings validation

[larsiusprime]

• load_settings() should return an instance of class Settings
• phase 1:
  • class Settings should inherit from dict and do nothing else special
  • ensure that works
• phase 2:
  • add a basic schema validator function after load_settings() is complete
  • define and populate internal member variables in a way that the auto-documentation can see
• phase 3:
  • move default population out of random functions and into the Settings object
  • test vigorously that this doesn't break anything

If a Settings object isn't the way to do this, we should do it some other way, this is the basic idea