* Generate screenshot images for markers
In some scenarios it might not be possible to use the preview video or
image of markers, i.e. when only static images are supported like in
Kodi. So generate a static screenshot as well.
* Make generating animated and static image optional for markers
* Use screenshot for markers when preview type is set to static image
* Make config instance-based
* Remove config dependency in paths
* Refactor config init
* Allow startup without database
* Get system status at UI initialise
* Add setup wizard
* Cache and Metadata optional. Database mandatory
* Handle metadata not set during full import/export
* Add links
* Remove config check middleware
* Stash not mandatory
* Panic on missing mandatory config fields
* Redirect setup to main page if setup not required
* Add migration UI
* Remove unused stuff
* Move UI initialisation into App
* Don't create metadata paths on RefreshConfig
* Add folder selector for generated in setup
* Env variable to set and create config file.
Make docker images use a fixed config file.
* Set config file during setup
