[Schematic] Add notes to overrides

"Hey guys, here's a feature request: Add notes to an override. Why the change? Who created the override?" Overrides are our most utilized feature, so this is a great idea! What are overrides? In many scenarios customers might need features or limit thresholds that don’t come standard in a pre-baked package. Examples... - Exceptions on an enterprise deal - Feature trials - Feature testing Our customers use Schematic to apply overrides individually to any company, or programmatically via our API. We also support time-limited overrides, which allow you to make a feature available, or bump a limit, for a limited period of time. Often useful in pre-sale or upgrade conversations.