Improve Internationalisation Support

[soceanainn]

Implement proper internationalisation support for this project.

Third-party libraries for managing internationalisation configurations exist (e.g. i18n-node), but might be overkill for the time being, in favour of using a default language (Irish), requiring users to manually select other languages. It should then be simple enough to storing all translation values in JSON files that can be loaded by either the server or by individual clients.

It might be necessary to introduce a templating engine (such as mustache) in order to define HTML in a more static way than dynamically generating all site text using JS on the client side.