Documentation should mention i18n_patterns and translation

[benjaoming]

It would be nice if the documentation in some way mentioned how to have a Wiki in different languages, for instance what happens with /en/wiki and /fr/wiki supposing it's available in English and French:

• How to using i18n_patterns, maybe this should be a real code snippet example in the main installation instructions since it's so commonly needed
• How to host content in different languages (hint: it's not really supported but easy to make a solution for it)
• How to make a language switcher (perhaps just link to a solution)