Update Single Pages dashboard controller to pass error codes rather than error messages
Fix messages in dashboard/pages/single

Let's use the standard message/error handling
Merge pull request #1 from mlocati/update-dashboard-single-page-errors-v2

Fix messages in dashboard/pages/single
Merge pull request #1625 from chriswayoub/update-dashboard-single-page-errors

Update Single Pages dashboard controller to pass error codes