Delete action. Does nothing (waiting for extension of NDBStore).
TODO: Delete search index.
For #40-expire-harvested-data
Deleting search index
For #40-expire-harvested-data
Use rdflib_appengine 1.1 to facilitate destroy() of a Graph
For #40-expire-harvested-data
Used delete action to create a refreshing scheme
Fixes #40-expire-harvested-data