Make original author look like commenter when reblogged

This wasn't as simple as changing the persona in the XML,
because the same layout is used for a post whether reblogged or not.
So the persona needs to be changed programmatically for reblogged posts.
For this, the `AuthorView#setPersona()` method has been made public and
was changed to always set all views into the desired state to support
usage in a RecyclerView.

![device-2016-11-21-094221](/uploads/e508937ad2d2d84f97f5be29bdeaac2e/device-2016-11-21-094221.png)

Closes #639

See merge request !426