Remove reference to mockup-core in getting started docs.
Remove reference to mockup-core in getting started docs.

plone/mockup,derFreitag/mockup,plone/mockup,derFreitag/mockup,domruf/mockup,derFreitag/mockup,domruf/mockup,derFreitag/mockup,domruf/mockup,domruf/mockup,plone/mockup