DateIntervalMapping i18n

* implement a "since xxx" construct common in Fr
* allow several words per language for "present"
* adding more languages in config file
* custom (textual) separators for DateIntervalMapping (language dependant): allows for "de ... à ..." used in Fr
* create unit tests
something like `( if (splitString == null) "" else "|" + splitString )` would also work so if you default it to ""
it'd change to `( if (splitString.isEmpty) "" else "|" + splitString )`