NeulandTox: Set default name and status message

Set a default name and status message when loading from a data file that
doesn't at least provide a name or when creating a NeulandTox instance
without data path.
NeulandApplication: Remove unused #define
Improvements on loading contacts

When loading from data, also restore the status message. Also, when a
contact has no name, show the Tox ID instead. This is important for
adding new contacts; they used to show up without any identity hint
before, until they came online and we got their name.