Subtitles with the same language code but different sub code are treated as duplicates

[rtibbles]

• ricecooker version: 0.7.0b6

Rather than allowing subtitles from multiple locales but the same language, ricecooker discards these as duplicates.

[nucleogenesis]

@AllanOXDi raised this in the planning meeting - just noting that this is back on our radar, but not a high priority.

@rtibbles does this complement or conflict with your ongoing Ricecooker refactors?

In any case, I'm not sure if/when this will become a priority, but perhaps in some downtime in the coming months, Allan and I can hack on this a bit together.