Add confirmation to cancel button

[nathankota]

Address the first caveat below (from #210). Anything else?

Caveats

1. There is no confirmation dialog safety right now
2. The data is deleted. only marked as deleted
3. All the supporting data is deleted
4. The final pdf doc is kept
5. An email is sent to UGRC

Originally posted by @steveoh in #210 (comment)