Error handling improvements (#71)

* Remove `emperror.dev/errors`, remove all `errors#Wrap` and `errors#WithStack` calls
* Improve logging in `server/backup.go`

config/config_docker.go

@@ -1,7 +1,6 @@
 package config
 
 import (
-	"emperror.dev/errors"
 	"encoding/base64"
 	"encoding/json"
 	"github.com/docker/docker/api/types"
@@ -73,7 +72,7 @@ func (c RegistryConfiguration) Base64() (string, error) {
 
 	b, err := json.Marshal(authConfig)
 	if err != nil {
-		return "", errors.WithStackIf(err)
+		return "", err
 	}
 
 	return base64.URLEncoding.EncodeToString(b), nil