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  for each application, job, task and the details of proportion of activity for each task.

I added 3 timeline features to existing Web UI.

[Application Timeline View]
This view shows following things.

* When each executor was added/removed and the reason why it's removed.
* When each job  was started/finished.
* Status of each job.

![screenshot from 2015-04-01 16 49 25](https://cloud.githubusercontent.com/assets/4736016/6936886/e35fd582-d891-11e4-980d-8de13f50e442.png)

[Stage Timeline View]
Similar to Application Timeline View, this view shows following things.

* When each executor was added/removed and the reason why it's removed.
* When each job was started/finished.
* Status of each stage.

![screenshot from 2015-04-01 16 50 59](https://cloud.githubusercontent.com/assets/4736016/6936900/0dca6526-d892-11e4-84a8-efd9037af444.png)

[Task Assignment Timeline View]
This view shows following things.

* When each task started/finished
* How long each task spent and the proportion.
* Status of each task.
* Where each task ran on.

![screenshot from 2015-04-01 16 51 54](https://cloud.githubusercontent.com/assets/4736016/6936910/20fd5acc-d892-11e4-9018-80e463881fc2.png)

All the view above is zoomable by mouse wheel action and scrollable by drag action.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2342 from sarutak/timeline-viewer-feature and squashes the following commits:

11fe67d [Kousuke Saruta] Fixed conflict
79ac03d [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
a91abd3 [Kousuke Saruta] Merge branch 'master' of https://github.com/apache/spark into timeline-viewer-feature
ef34a5b [Kousuke Saruta] Implement tooltip using bootstrap
b09d0c5 [Kousuke Saruta] Move `stroke` and `fill` attribute of rect elements to css
d3c63c8 [Kousuke Saruta] Fixed a little bit bugs
a36291b [Kousuke Saruta] Merge branch 'master' of https://github.com/apache/spark into timeline-viewer-feature
28714b6 [Kousuke Saruta] Fixed highlight issue
0dc4278 [Kousuke Saruta] Addressed most of Patrics's feedbacks
8110acf [Kousuke Saruta] Added scroll limit to Job timeline
974a64a [Kousuke Saruta] Removed unused function
ee7a7f0 [Kousuke Saruta] Refactored
6a91872 [Kousuke Saruta] Temporary commit
6693f34 [Kousuke Saruta] Added link to job/stage box in the timeline in order to move to corresponding row when we click
8f88222 [Kousuke Saruta] Added job/stage description
aeed4b1 [Kousuke Saruta] Removed stage timeline
fc1696c [Kousuke Saruta] Merge branch 'timeline-viewer-feature' of github.com:sarutak/spark into timeline-viewer-feature
999ccd4 [Kousuke Saruta] Improved scalability
0fc6a31 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
19815ae [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
68b7540 [Kousuke Saruta] Merge branch 'timeline-viewer-feature' of github.com:sarutak/spark into timeline-viewer-feature
52b5f0b [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
dec85db [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
fcdab7d [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
dab7cc1 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
09cce97 [Kousuke Saruta] Cleanuped
16f82cf [Kousuke Saruta] Cleanuped
9fb522e [Kousuke Saruta] Cleanuped
d05f2c2 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into timeline-viewer-feature
e85e9aa [Kousuke Saruta] Cleanup: Added TimelineViewUtils.scala
a76e569 [Kousuke Saruta] Removed unused setting in timeline-view.css
5ce1b21 [Kousuke Saruta] Added vis.min.js, vis.min.css and vis.map to .rat-exclude
082f709 [Kousuke Saruta] Added Timeline-View feature for Applications, Jobs and Stages