Combine getLanguageNames and getTranslatedLanguageNames into one function which is...

Combine getLanguageNames and getTranslatedLanguageNames into one function which is much easier and more logical to use. Does not contain any actual changes yet in what the function does.
* Reduces the overly long code in r107002, and reduces code for {{#language:}}
* Fixes the language list in Special:Translate which contained languages that gave "invalid code" when selecting