Language support

Concentrate on localising the user interface at the moment (i.e. don't bother with the help yet).

• start using crowdin.net project - as a subdomain : http://translate.multibit.org
• target languages for MultiBit 0.2.0: en, es, fr, it, ru, sv, no
• Improve properties so that the number of languages and list of language codes is just in one file somewhere. It is currently repeated in all.