Dataset existing error should point to location

Then the creation scripts can still ask for information about the
dataset and certificate.
Merge pull request #939 from theodi/feature-include-existing-dataset-url

Include dataset url in duplicate response
Paginate and only load necessary datasets on dashboard
Merge pull request #941 from theodi/hotfix-dashboard-load

Paginate and only load necessary datasets on dashboard
Report published datasets with certificates
Merge pull request #942 from theodi/feature-dashboard-certificate-info

Report published datasets with certificates