Theme settings disable functionality

Using the theme configuration, themes should be able to disable some ghost blog functionality.

Example:
An old theme that does not yet support new ghost versions should be able to disable things like image sizing, etc.

An old theme that does not yet support new ghost versions

If a theme doesn’t support the available features in a version of Ghost then it’s not compatible with that version and you will get appropriate warnings/errors when installing it.

Old themes won’t know what future features will be available so it’s not possible for them to pre-emptively disable core Ghost features. Having core features enabled/disabled without the user’s consent also creates expectation, documentation, and support problems so it’s not something that would be implemented without serious consideration to knock-on effects.