Return permission error as json for ajax requests

**Issue**
I installed a demo site. When I log in as demo user in the administration it throws 2 json parse errors for the ajax requests it does for the map and the chart. The demo user has no permission to see the data so instead of a json response it sends the whole Access Denied Page.

**Fix**
(in admin/error/permission)
I added a second array with ajax routes and a function to send the permission error as a json response to pages in this array.

**Complications**
Since it sends no data to the chart engine it throws a javascript error which is addressed in a separate pull request -> gortsilas:chart-no-data (#2415)