Dashboards: Have setting to email dashboard json automatically upon deletion

**Why is this needed**: Grafana has added many features to facilitate dashboard recovery. However, it still can be an issue where users delete dashboards they later want to re-add, which can result in support tickets or other issues trying to recover the dashboard. **What would you like to be added**: Have an admin level setting to define if dashboards, when deleted, should have their json be automatically emailed to one or more admin accounts. What account could maybe be defined too, as perhaps a shared email list could be that contact point. This would allow users who frequently encounter this problem the option to self-service. Another option might be emailing the deleted dashboard json to whoever deleted it. This would limit impact to one person, but some users may want a copy to be sent elsewhere. **Who is this feature for?** Users who delete, and then want to recover, their dashboards.