Remove hardcoded vocabulary ids

[DavidLeoni]

There are a few places where this happens, and I don't understand well how vocabularies work

[DavidLeoni]

Some info about vocabularies from Gabor:

the vocabulary id is a numerical code for a language.
it is preferable to use the language code whenever possible, as it is standard and human-understandable while the vocabulary id is not. furthermore, the vocabulary id may change across UKC versions.

there is just one case where you should prefer the vocabulary id: if using the language code leads to lots of extra web service calls, in which case you may cache and reuse the vocabulary ids.