[lng] Add missing translation strings + small fixes

This adds the missing translation strings for the module. Now it should be translatable to any language.

It also converts all the buttons to use the latch style instead of plain HTML. Now all buttons will use this style:
![platch-button](https://cloud.githubusercontent.com/assets/1119272/2666806/dd59a570-c0a3-11e3-874e-d6da3e46ff57.png)