UserStream: Fix indentation
UserStream: Take an Account instance and not just its name
Save the friends array for a accounts
ComposeTweetWindow: Put the buttons in a GtkHeaderBar

... if the settings say so.
SearchPage: Don't show the "load more" button too early

All widgets in our list will be shown in show_entries, which will be
called once the Collect object has signalled that all tasks have
finished.