Setup and migration UI refactor (#1190)

* 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

pkg/api/resolver_mutation_plugin.go

@@ -23,6 +23,7 @@ func (r *mutationResolver) RunPluginTask(ctx context.Context, pluginID string, t
 		}
 	}
 
+	config := config.GetInstance()
 	serverConnection := common.StashServerConnection{
 		Scheme:        "http",
 		Port:          config.GetPort(),