support hiding plugins

[bengreenier]

Currently all plugins that exist are loaded and must exist somewhere on the grid. This is clearly undesirable. 🛩

[bengreenier]

see https://github.com/bengreenier/overlayed/tree/feature/hide-plugins for some wip here...but there's an RGL issue that forces us to wrap everything in divs and therefore prevents the approach used on that branch from working properly

[bengreenier]

this works today, but the setting is perhaps in a confusing location that people might not expect...namely under pluginName: instead of under layout: [].