[URGENT] [TBR] Restructure concert schema

- Add hasTimes field to concerts in the JSON schema
- Adds begins field to songs in the JSON schema
- Shows these times in the frontend
- Shows a warning message about the concert cancelation and the virtual
  concert planing
- Add CLI tool to get songs by person (tools/list.php)

Change-Id: Iec80ceb69e1a45cd467aaeaa59337a9966c78b7c
7 files changed
tree: 2a71159c2bc7c6447d67cd539fdd93a460e09685
  1. concerts/
  2. css/
  3. img/
  4. js/
  5. tools/
  6. index.html
  7. manifest.json
  8. robots.txt
  9. sw.js