Added JSInput template in Studio. [BLD-523]

@auraz @singingwolfboy please review. This PR adds a template for JSInput that loads a simple WebGL demo. The shapes can be selected and a correct answer will be generated if the cone has been chosen and not the cube. That's in theory, it will not work for the moment, as SOP gets in the way. The application files are situated in in the assets of the DemoX course (like the image in the image response template):

https://studio.edx.org/c4x/edX/DemoX/asset/

I think the application's HTML+JS+CSS files belong there. Should we circumvent SOP by modifying slightly JSInput with a library like easyXDM (http://easyxdm.net/wp/)? We've already run into problems with JSInput and SOP before, while integrating jsVGL for 7.00x. It was solved by using the <add-linker name="xsiframe"/> flag for the GWT compiler:

https://edx-wiki.atlassian.net/wiki/display/BLD/jsVGL+integration