[#170] Support .tar/.tgz unpacking during upload

During upload if X-Explode-Archive is set, gate tries to read archive and create an object for each file.
Each object acquires a FilePath attribute which is calculated relative to the archive root.
Archive could have compression via Gzip if "Content-Encoding: gzip" header is specified

Signed-off-by: Nikita Zinkevich <n.zinkevich@yadro.com>

internal/handler/multipart.go

@@ -42,7 +42,9 @@ func fetchMultipartFile(l *zap.Logger, r io.Reader, boundary string) (MultipartF
 		// ignore multipart/form-data values
 		if filename == "" {
 			l.Debug(logs.IgnorePartEmptyFilename, zap.String("form", name))
-
+			if err = part.Close(); err != nil {
+				l.Warn(logs.FailedToCloseReader, zap.Error(err))
+			}
 			continue
 		}