Apply LanguageFallback (variants) for getLabel in lua

we had this before we changed to use the label lookup.

maybe we also want a method to request labels without
resolving fallback or something else? regardless of
whatever / however else we want, i think we should
keep getLabel behavior consistent with what it was before.

also add test case to check that language fallback is
applied for lua entity serialization for variant languages.

Change-Id: I07e698b9fec99c612f0d52fc337396360b765b66
Merge "Apply LanguageFallback (variants) for getLabel in lua"