initial fix in order to split translation file and allow full text customization

initial fix in order to split translation file and allow full text customization

this pull request is not yet ready to be integrated as it lacks simply the translation array fusion on the GLC.

@vecna / @fpietrosanti / @hellais what do you think of this solution?

we now have a single JSON file for wach language: https://github.com/globaleaks/GLClient/tree/feature/translations_customization/app/scripts/l10n

each file contains a dictionary indexed by the original english sentence embedded inside the code.
the power of this solution is that:
- a single language can be updated by replacing the respective file.
- the client can fetch only the interesting translations using a lazy loader starting from the current languade and making a simple fusion of the different files (a simple additive sum)
- also english can be customized.