Support content imported fom Confluence with translation migration support enabled

This ticket is more like a heads up.

Confluence-XML now imports translated content using XWiki's native localization features by default, where each translation has its own localized document instead of having language macros  all in the same document (the translatedContent macros in book versions).

See CONFLUENCE-486.

This support can be disabled at import time to use the old behavior but it would be nice not to have to do this.