hidden settings

[UziTech]

Summary

Allow certain config settings to be hidden from the settings panel.

{
	"config": {
		"someSetting": {
			"type": "boolean",
			"default": false,
			"hidden": true
		}
	}
}

Motivation

Packages sometimes need to save configuration that the user shouldn't change. It would be nice to keep that in atom.config but not show it in the settings panel.

Describe alternatives you've considered

Right now we just use an automatically collapsed object to hide the settings but they can still be shown.

[UziTech]

@Arcanemagus Are you able to review #1144 or do you know who can?