Bug fixes

Bugfix for 3158330 - Error when media item does not exist

Issue #3169542 by jurgenhaas: Add support for content chains in schedule generator
Issue #3173812 by jurgenhaas: Declare all routes as admin routes
Issue #3174081 by jurgenhaas: Add support for javascript
Issue #3174095 by fhaeberle, jurgenhaas: Action buttons in preview mode
Issue #3174098 by jurgenhaas: Local schedule doesn't get reset after content change
Issue #3177903 by jurgenhaas: QR code to self
Issue #3178106 by jurgenhaas: Provide option for content to extend duration of a slide on the fly

Issue #3177358 by jurgenhaas: Load javascript files separately
Issue #3177738 by jurgenhaas: Workaround json load limitations
Issue #3178147 by jurgenhaas: Use API endpoint for resolved promise of current slide
Issue #3179235 by jurgenhaas: Loading QR code as an image fails
Issue #3179364 by jurgenhaas: Improve image link recognition by using DOM
Issue #3179444 by jurgenhaas: Controll links to open browser and then close it again
Issue #3179642 by jurgenhaas: Support digital signage overlay framework