Localization source

[NoxMortem]

According to #146 the localization stores the page number but it should also get a source field as e.g. german and english as well as .pdf and print books do differ and not all information is simply in both "print" version on different pages.

[UrsZeidler]

In the chummer resources they simply use an other source book, and as we import/transform these resources we also have a german core rule souce book, and I'm not sure there should be objects with linked with the german source book.