More error handling improvements
Catch no-op crop parameters
web: Refactor client-side model API in preparation for better error handling
web: Error handling for shutdown/reboot
web: Simplify error response handling
web: Move modals/overlays to external layer
web: Use check_call instead of call for shutdown/reboot
web: Set _layer to null after removing it
web: Fix log download (fixes #121)
web: Fix some minor omissions/typos