Localized error messages

[zml2008]

Configuration error messages are often visible to end users, whose primary language is not English.

We should make every error message translatable - limited by underlying libraries

This can work using the standard Java ResourceBundle system, and must work standalone.

We can hopefully build on Sponge's existing use of crowdin by adding a project to help process user-submitted translations.

It would be nice to provide some sort of hook so translations can be expressed in a native-friendly way-say, with Minecraft's chat components, to display localized error messages ingame in the client locale, rather than the server locale.