Allow specifying exact language for lyrics

[riipah]

Same as #10, but for lyrics. It should be easier to implement this just for lyrics because lyrics are not used for searching. Lyrics are also more commonly provided in multiple languages, so specifying the language for them might be more useful than for titles.

Regarding how this would work with the current language option for lyrics

The editor should still be able to input Romanized lyrics. Obviously Romanized isn't a proper language. We could offer options for "Original", "Romanized" and "Translated" in addition to the selection for the specific language.

UI suggestion: fixed fields for original and romanized. Variable number of fields for translations. Language can be selected for original and translations, but it's not necessary for romanized. Is one field for original and romanized enough? The list of languages could be the same that can be selected for user's "languages I know" list.

Mapping from current content language selection:

Content language preference	Content language selection	Translation type + language
Original	Matching default name language	Original
Non-English	Non-English	Original, unless it's English, otherwise first translation (see below for preference)
Romanized	Romanized	Romanized
English	English	Original if it's English, otherwise English translation
-	Unspecified	Translation

How the lyrics are displayed on the song page

If the lyrics are translated to many languages, this would convolute the lyrics tab on song page, so we need some solution to avoid that. Maybe the most common language options (original, romanized, English) could be displayed first, and then other languages in a dropdown or similar.

We could match the lyrics language to user's display language, or their known languages, and display translation for that language first.