QueryManager: cleanup active vs running, fix kill

1. In an earlier commit, I confused the notions of active queries (running, queued)
   with running queries. Rename 'activeQueries' to 'runningQueries' to explain
   the difference.

2. The user should be able to kill a queued query. Thus, make the 'kill(qId)' API
   call look at all active, not just running, queries.

3. Add the ability to kill/cancel queued queries.
QueryQueueTest: test canceling a query in the queue
Merge pull request #645 from uwescience/fix-643

Fix 643