Feature: Branching and merging

[marcelklehr]

You don't always want people to have immediate writing access to the document, but rather be notified of a suggested change. Fiduswriter allows the document owner to restrict edits to the user's own branch and only overtake them to the owner's document manually.

The question is how to identify edits that should go into the same branch and how to integrate this feature with the different editors that hive.js supports.

[marcelklehr]

If this becomes a plugin, it depends on #21