Nucivic open data schema map issue 37 group list endpoint

NuCivic/nucivic-internal#37

This PR depends on ed8cdbfeb6a36c8e31beafa48586cea7eecdd318 NuCivic/nucivic-internal#36  

###Accepting test

Remove harcoded group list from dkan_dataset_api.module 
Clear cache
When I go to /api/3/action/group_list I should see a list of sluggified items inside the results key