Display names in the contacts list instead of email addresses where possible

This is the work for [this card](https://trello.com/c/OsTAnoeO).

It is split up into three changesets:

1) a82da26 Removes redundant code
2) 11da1d4 Renames 'nick' to 'username' in the frontend, so this matches what the worker has in its object.
3) 42f68ef Implements the functionality to send all user information from the worker to the sidebar, and then display that information in the sidebar itself.

Suggest review from @n1k0