Fixed translations

* bnc#878606 - hard-coded ERB has been moved to a separate file
* This also required https://github.com/yast/yast-rake/pull/7 (already merged)
* bnc#881277 - textdomain definition was missing
* This also required https://github.com/yast/yast-devtools/pull/55 (already merged)
Probably not but it was there so I only moved it. I can probably remove it.