Layout validation

So the layout would be considered "invalid" in that case - ie there are missing files needed to show it, and it wouldn't be considered to be shown from the schedule

• If there are multiple layouts in the schedule, for now, the Player would check those in the same way, and if one or more of them were valid those would be shown
• If nothing is valid, then the default layout is shown
• If the default layout is invalid, then a hard-coded splash screen layout (the other players use layout id 0 which they have locally in their resources) is shown instead