Display dialect_name

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We sometimes have dialect glottocodes i the dialect field; maybe these should be displayed too? But:

• Glottolog doesn't do anything with them (although eventually we might want to have good dialect coverage of widely geographically distributed languages, in which case we'll have to add location data for dialect glottocodes, whether by forking Glottolog or maintaining our own repo - we don't want American English showing up in England, or Mexican Spanish showing up in Spain)
• Glottolog doesn't always have dialect glottocodes for the dialects in question (e.g. dzal1238-1 and dzal1238-2, Southern and Northern Cuona)
• Sometimes sources call something a dialect and Glottolog calls it a language; since we follow the source in naming, we use dialect_name, but since we follow Glottolog in glottocodes, we don't use dialect