Feature i18n

This request includes all needed commits to enable i18n on LibraryBox V2. 
- the [web10Ln](https://github.com/fabi1cazenave/webL10n) library
- En and Fr translation files, located in the locales directory. Language files loaded by the library depending on the browser's language

As is, the library is setup for verbose logs (seen in the browser's console, not in the application itself). This behaviour can be changed by setting the value of the gDEBUG var in l10n.js