Reporting of content group templates

Add functionality to report content group templates

Add new menu item to content group template preview more menu for reporting it. For this open a dialog.

Create ViolationReportComponent for this in which you can select a reason and enter a description.

Add management for reports to admin interface

Create new route /reports in which reports can be managed. Open reports can be dismissed or confirmed.

Show target type, reason and description for reports. Also add link to the target.

For closed reports hide buttons and show decision.

Depends on arsnova-server!727 (merged), !1898 (merged)

Closes #1218 (closed)