Add kill and cancel functionality to UI

Add kill links (like in the Spark Web UI) to each session in the All Sessions Page
• Include popup verification (like in Spark)
•

 Calls DELETE /session/{id} 

Also add similar cancel links to each statement in the Session Page
• Include popup verification
•

 POST /sessions/{sessionId}/statements/{statementId}/cancel 

These links should require proper security

[This may be split up into two PRs if needed]