Implements new Configuration API

closes #3619
- adds new permissions for configuration API
- adds integration tests
- adds configuration API for reading allowed values
Restrict uncapitalise middleware for API

no ref
- Do not lowercase anything after /api/v0.1/<resource>/ to protect :key/:slug
Merge pull request #3898 from halfdan/fix-uncap-api

Restrict uncapitalise middleware for API
Merge pull request #3841 from halfdan/3619-configuration-api

Implements new Configuration API
Update About page styles

References #3568 & #3575

With the move to new global styles, the about page styles got a bit borked. This fixes those.