Added template for iFrames. [BLD-611]

The template loads a simple geometric, interactive JS application based on JSXGraph:

http://jsxgraph.uni-bayreuth.de/wp/

called Euler line:

http://jsxgraph.uni-bayreuth.de/wiki/index.php/Euler_line

It was slightly modified, the zoom bar and copyright text were hidden. The application resides on the assets of edX's Demo Course:

https://studio.edx.org/c4x/edX/DemoX/asset/eulerLineDemo.html
https://studio.edx.org/c4x/edX/DemoX/asset/jsxgraph.css
https://studio.edx.org/c4x/edX/DemoX/asset/jsxgraphcore.js

License of JSXGraph is compatible with the edX platform, LGPL 3 or MIT.