[WIP][SPARK-3468] WebUI Timeline-View feature

I sometimes trouble-shoot and analyse the cause of long time spending job.

At the time, I find the stages which spends long time or fails, then I find the tasks which spends long time or fails, next I analyse the proportion of each phase in a task.

Another case, I find executors which spends long time for running a task and analyse the details of a task.

In such situation, I think it's helpful to visualize timeline view of stages / tasks / executors and visualize details of proportion of activity for each task.

Now I'm developing prototypes like captures I attached.
I'll integrate these viewer into WebUI.

[Capture of prototype for Stages timeline view]
Each brown bar represents submission time to finish time of a stage.

![stages](https://cloud.githubusercontent.com/assets/4736016/4212893/e1cb20c0-38a8-11e4-91bc-a20042b109fb.png)

[Capture of prototype for Task timeline view]
Each brown bar represents launch time to finish time of a task.

![tasks](https://cloud.githubusercontent.com/assets/4736016/4212914/4f201432-38a9-11e4-91e9-9c2030991468.png)

[Capture of prorotype for Task details view]
This shows the proportion of activities in a task.

![taskdetails](https://cloud.githubusercontent.com/assets/4736016/4212921/74943fe0-38a9-11e4-86ac-8f9f9f6e65c7.png)

[Capture of prorotype for Executor timeline view]
Each brown bar represents start time to finish time of a task which a executor executes.

![executors](https://cloud.githubusercontent.com/assets/4736016/4212925/a3bb78ec-38a9-11e4-8909-9d662d8d6093.png)