Support customising the unicorn worker processes for collections
Support customising the unicorn worker processes for collections

As we're seeing warnings about more than 2 established connections to
collections. The frontend machine seems to have enough memory, so
support increasing the number of workers.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet