Add a targeted data deletion capability

[n3101]

Describe the new feature you'd like
Add the ability to identify specific data vertices, or categories of vertices, and delete them from a persisting backing store.

Why do you want this feature?
Graphs may hold data which is now unwanted, or should not have been added in the first place.

Describe alternatives you've considered
At present these items can only be removed before they reach their age-off date by working directly in Accumulo or manipulation of the Gaffer schema to exclude them. Neither or these is convenient and the latter risks permanent loss or damage to the rest of the data.

Additional context
See also internal documents.

[cn337131]

Issue addressed in issues #3238 and #3237 and their associated merges.