Don't require i18n source files to be encoded.

Currently, the i18n files need to be encoded, as Java can't process UTF-8 property files properly. See https://stackoverflow.com/questions/4659929/how-to-use-utf-8-in-resource-properties-with-resourcebundle for some background.

Having encoded files in our source prevents people from quickly making changes.

We should apply encoding during the build process, allowing non-encoded files in our source.