![screenshot from 2015-01-16 13 43 25](https://cloud.githubusercontent.com/assets/992952/5773256/d61df300-9d85-11e4-9b5a-6730058839fa.png)

This is a first step towards having time remaining estimates for queued and running jobs. See SPARK-5216

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #4043 from ScrapCodes/SPARK-5216/5217-show-waiting-stages and squashes the following commits:

3b11803 [Prashant Sharma] Review feedback.
0992842 [Prashant Sharma] Switched to Linked hashmap, changed the order to active->pending->completed->failed. And changed pending stages to not reverse sort.
c19d82a [Prashant Sharma] SPARK-5217 Spark UI should report pending stages during job execution on AllStagesPage.