Bulk delete activity instances from scheduling goal

[bashbash]

srschaff https://jira.jpl.nasa.gov/browse/AERIEQS-381 Moderate I would like a convenient way to bulk delete all of the activities created by a given scheduling rule. This is especially relevant when re-running a scheduling rule after other plan changes, since we will want to clear out the previous instances to make room for the scheduler to add new instances.