Flag for disabling all default rules

[myzozoz]

Motivation

Right now default rules can be overridden by adding a custom rule with the same name. However, if there are many default rules and the user wants to get rid of all of them, then writing a lot of dummy overrides becomes laborious and ugly code.

Solution

Add a flag that disables all default rules. Suggested location is the MLproject file.

[myzozoz]

Since opening this issue, we have moved away from using the MLproject file for passing inputs and the implementation should accordingly use the new GitHub action way of passing inputs.