Add "Kill" and "Kill & Scale" buttons for tasks

Make task rows clickable in order to "Kill" and "Kill & Scale". Multiple tasks can be killed at once, but kill & scale is currently only implemented for one task at a time due to issue https://github.com/mesosphere/marathon/issues/108. By allowing only one at a time, it throttles the requests and ensures the scaling happens properly.

Also make all table rows look clickable with pointer cursor since they are actually clickable.

Refresh/View:
![screenshot 2014-01-13 19 07 20](https://f.cloud.github.com/assets/29612/1907359/2130b8d4-7cc9-11e3-91d0-b4935c7acee1.png)

Kill and Kill & Scale:
![screenshot 2014-01-13 19 07 26](https://f.cloud.github.com/assets/29612/1907361/300f9d16-7cc9-11e3-89bd-35fc784b6cdf.png)