SPARK-2115: Stage kill link is too close to stage details link

Moved (kill) link to the right side. Add confirmation dialog when (kill) link is clicked.

Author: Masayoshi TSUZUKI <tsudukim@oss.nttdata.co.jp>

Closes #1350 from tsudukim/feature/SPARK-2115 and squashes the following commits:

e2263b0 [Masayoshi TSUZUKI] Moved (kill) link to the right side. Add confirmation dialog when (kill) link is clicked.