Add i18n support in the datatable wrapper

[EitanBlumin]

Base:
https://datatables.net/manual/i18n

• Add "language" element to the respite_crud static class in datatable_respite_crud.js
• Add static function to translate a string based on the language element. If not found in element, return original string input, but log warning in console about the missing translation.
• Replace all literal strings used in the script with the translation function, and add each such string to the language element.
• Add an Ajax function to load a json file to use as language element, same as in datatables.