Set up unicorn config for govuk_app_config
Set up unicorn config for govuk_app_config

This uses the shared configuration provided by govuk_app_config. I went
out on a limb and decided it was unlikely this app needed to be special
and have the working_directory value set. I couldn't find any evidence
this was required and hopefully if it is we'll find out pretty quick and
can provide the reason in the commit message (which is long lost
currently).

alphagov/frontend,alphagov/frontend,alphagov/frontend,alphagov/frontend