Make it possible to start briar with temporary account with a bunch of testing contacts

comment by @sebkur :

Next to that, I think it makes sense introduce a few testing classes in src/test that are not unit tests which check if some method succeeds, but instead have a main method that start briar in a certain configuration. For example one of those entry points could start briar, create a temporary account with a fixed password with the database stored at an appropriate temporary directory and sets up 10 or so fake testing contacts. That will make it very easy to experiment with changes made to the UI. (See #59 (closed))