skos-label: should respect inherited language

[nichtich]

If not lang attribute is specified, the language could be searched for at the parent elements. See jQuery implementation of :lang(). In addition the browser language could be queried, as implemented [http://angular-translate.github.io/docs/#/guide/07_multi-language](in angular-translate) with method determinePreferredLanguage().

The observer could call this code on each $digest loop to detect language changes, but watching all parent elements might be quite slow. Passing language attributes from one element to another, however, might be slow as well.

See also

• http://stackoverflow.com/questions/20444578/get-current-language-with-angular-translate
• http://stackoverflow.com/questions/21332671/angularjs-watch-dom-change