Add a field denoting Administrative level to VizAlertsConfig workbook

[mcoles]

See https://community.tableau.com/message/577785

The subscriber_license field in VizAlertsConfig workbook only indicates whether the user is licensed, and if so, what it is. It doesn't describe the Admin level of the user, despite several examples showing it being used that way.

Thus, we should add a new field to the VizAlertsConfig workbook that denotes the subscriber's Admin status. The calc used in the Shareable Data Sources for Tableau Server post could be re-used.

[mcoles]

Adjusting the example calcs in VizAlertsConfig workbook for 2.0.1. We can add the new field in 2.1.0.