Add video upload feature to Studio

This still needs to be audited for accessibility.

Please review: @nasthagiri @andy-armstrong @frrrances @talbs 
FYI: @clrux @doctoryes @karadhya 

*JIRA Tickets:*
* https://openedx.atlassian.net/browse/MA-28
* https://openedx.atlassian.net/browse/MA-85
* https://openedx.atlassian.net/browse/MA-86

*UX Design:* https://edx-wiki.atlassian.net/wiki/display/UX/Video+Uploads+in+Studio
*Functional Spec:* https://openedx.atlassian.net/wiki/display/MA/Video+Pipeline
*Sandbox:* http://studio.video-pipeline.m.sandbox.edx.org/

I'm not sure about these usages of ```gettext_noop```. If you switch on the test Esperanto language, it seems that the strings defined using it do not get translated:

http://studio.video-pipeline.m.sandbox.edx.org/videos/vpip/vpip/vpip?preview-lang=eo

![image](https://cloud.githubusercontent.com/assets/5985072/5311071/bf29072e-7c0c-11e4-908d-6aa376e05555.png)