New config integration work.

Replaces PR #382, in addtion to @jodal's work this does:

- Splits load config into load and validate
- Makes logging a bit less noisy and more usefull at debug and info levels
- Filters out disabled extensions
- Makes lists config values into tuples so we don't have mutable config.
- Added list settings and killed the old one
- Added flag based config overrides
- Collects errors for all sections, not just first one to fail.
- Remove ext. prefix from configs.
- Starts passing new config values to systems that need them.