CYB-386 Clean generic URLs in Thor

* adds the 'generic_urls' table to the list of tables cleared by the task.

https://jira.ets.berkeley.edu/jira/browse/CYB-386
Merge pull request #237 from coyote/1.0.1/CYB-386_clean_generic_urls_in_thor

CYB-386 Clean generic URLs in Thor