add js uploader option to kaltura settings

closes CNVS-12148

test plan:
  - as an admin
    - navigate to plugins/kaltura
    - enter appropriate kaltura settings
    - at bottom of the form select option for html5 uploader
  - as an instructor
    - create an online submission assignment
      - enable Media Recordings under Online Entry Options
  - as student
    - navigate to previously created assignment
    - click Submit Assignment
    - test uploading files from both the RCE button and Media tab
      - verify that uploading works as before

  - with html5 uploader disabled
    - verify that flash uploader continues to work as it did prior

known limitations:
  - html5 uploader does not have a way to filter possible file
    selections the way the flash uploader does. to compensate it will
    check the file type to verify audio / video files.

Change-Id: I53b34f34c6b50b6f2fa45a9cc8ebfd00a80c7eda
Reviewed-on: https://gerrit.instructure.com/32849
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Bracken Mosbacker <bracken@instructure.com>
QA-Review: Nathan Rogowski <nathan@instructure.com>
Product-Review: Jason Madsen <jmadsen@instructure.com>