For matches with no recommendation, import as-is or skip automatically.

Add `import: none_rec_action` setting with a default of "ask" (current
behaviour). If set to "asis" or "skip", matches with no recommendation will be
imported as-is or skipped automatically.

This makes an interactive flow much more flexible and much easier when you are only interested in strong and medium recommendations, but don't want to lower the strong recommendation threshold and potentially accidentally auto-tag some albums incorrectly.