Improve the handling of special disabled features

[Alathreon]

Is your feature request related to a problem? Please describe.

Disabled features have two cases, normal features and special features. Special features are disabled with a string, which can be anything (usually a string representation of the class). But it is also error prone and not very good with features that are shared by several classes.

Describe the solution you'd like

Special features will now use an enum that will be filled with features.

Note that it will require to update the config for the special features (or the special features will be turned on, or the config parsing will crash).

Describe alternatives you've considered

Additional context