Audit Trail

Creates a history directory in the evaluate program's input folder. Giving the competition owner a way to look at a participant past output files. Giving them a running trail of what has happened before.  
Resolves codalab/codalab#436
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Example of the file output during compute worker running the scoring program. 
In the below case. Submissions for only phase 4 and submission 1 and 2 failed. 3 and 4 where success. thus their history is part of submission 5's history. 
![History folder example](https://cloud.githubusercontent.com/assets/123099/3236624/ccf02332-f0df-11e3-98b5-05d26634582a.png)
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**Please note:** 
these initial commits were cherry picked from 
https://github.com/Tivix/codalab/tree/feature/audit-trail
Which was accidentally branched from phase to phase. 

also suggest adding w=1 to the GET param's of this PR to remove showing whitespaces. 
Two comments:
- Right now, I don't think that we've made it possible for even the competition owner to download this file. Presumably, access would be added in the submissions views under MyCodaLab > Competitions that I'm managing.
- get_file_for_download would have to consider a new case to handle private output because only the competition owner should be able to download it. 
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