Add support for alternate language representation of a comment

[ltogniolli]

Currently multi-language posts are often created on steemit by intermixing both languages in the same document example. This is not an ideal format for readers of either language.

Once steemit.com supports specifying language a post is written in (see steemit.com/issues#300) it should be possible to link different language representations of the same content as such in the blockchain.

Ideally this should be done in a way that a user could set his preferred language in the frontend and the proper content should be served to him if available.

Possibly votes for an alternate representation of a content should be counted along the main content. If a different user submits a translation of an existing article, it should be represented similarly to a child comment in the blockchain (but not in the frontend).

[mvandeberg]

This could be handled by uploading repeated copies of the content and then defining metadata to instruct proper reading of the text. The blockchain supports full UTF-8. As this can be implemented using the existing tools and does not effect consensus, I am closing this ticket.