Use layers.json file from UCSC for testing
Move layers.json schema to separate file, and refactor
Handle "isNew" in layers.json

* Highlight "new" nodes if today's date is between specified start and end dates
* Highlight via bold text
* If a node is marked "new", highlight all ancestors as well
* If a container node is marked "new", highlight all descendents
* AGS service nodes can specify a list of "new" layer IDs