VizAlerts workflows (i.e. chaining actions, VizAlerts as IFTTT)

[jdrummey]

The idea here is to enable relatively simple chaining of actions into workflows. A couple of examples:

On condition X VizAlerts will download a workbook from dev, change data sources in the workbook to point to production, publish the workbook to production, and send out a notification on success/failure.

On condition X VizAlerts will send out advanced alert views to designated recipients, on condition !X VizAlerts will send SMS notifications to designated recipients. This is one we can do now inside a single advanced alert by playing with the Email Action & SMS Action fields, or via multiple advanced alerts.

Other workflow actions besides downloading a workbook, updating data sources in a workbook, and publishing a workbook might include running arbitrary Python/PowerShell/batch script code, updating parameters in a workbook, triggering an IFTTT action see #73, changing Tableau Server settings (or even restarting Tableau Server), etc.