Fix getAnswerFor and translations

Hi, i've made two main things:
* fixed getAnseweFor: added handling for selectionBox fields.
* Fixed some translations: added new, and fixed rebuild script.
There is a problem with the plonesurvey-plone domain. The rebuild script doesn't work for this domain, and i don't know if we still need it.
If i fix the script, a lot of translations for plonesurvey domain will be duplicated in that domain.