* Fix error string capitalization
Error strings often follow another string. Hence, they should not be
capitalized, unless referencing a name.
* Uncapitalize more error strings
While here, use %v on the error directly, which makes it easier to wrap
the error later with %w if need be.
* Uncapitalize more error strings
While here, rename Url to URL as a nitpick.
* 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
