Added last function for alerting conditions

Merge branch 'alerting_pagerduty' of https://github.com/utkarshcmu/grafana into utkarshcmu-alerting_pagerduty

Removed invalid alerting state from the UI

Update github auth docs

Add AWS Govcloud Region

Reduce alerting states

closes #6488

ref #6444

Removed playlist item when dashboard is deleted

ref #6444

In Github's "allowed organizations" scenario, it makes sense to have
`allow_sign_up` to be `true` as most administrators will expect their
org's github users to be able to sign in without further steps like
creating a local user first.