refactor feature database models

[onerandomusername]

After thinking about it for a while, features should exist in two tables: one which stores metadata about each individual feature, and the other which maps discord IDs to whether or not a feature is enabled.

An IDs to feature table where feature names are the columns and the ID override is a true/false/null for each column

Futher thought is required on whether or not getting the guild features with the config makes any sense.