Rewrite settings.make_app_settings()
Rewrite settings.make_app_settings()

- Remove `parse` option; I'm not sure why we wouldn't want to parse
  the settings, and the no-parse functionality isn't used anywhere.
- Remove `prefix` and `strip_prefix` options. I'm not sure how these
  would be useful in this context.
- Add a note about the `defaults` keyword arg to the docstring.
- Simplify internals so it's easier to reason about what's happening. In
  particular, build up the settings dict in order of priority--i.e.,
  add defaults from file, passed defaults, passed settings, then extras.
- Use the passed conversion map when reading the core defaults file.

TangledWeb/tangled.web