Updating JSXGraph

Since the stack-js update, we have been able to use JSXGraph in its released form.

The files related to it are now stored under corsscripts/.

Download JSXGraph from here: https://github.com/jsxgraph/jsxgraph.

The files one needs to copy over are jsxgraph.min.css and jsxgraphcore.min.js, there is no need to copy the non minified versions.

The old STACK side jsxgraph.js that provided the stack_jxg features is now called stackjsxgraph.js and is being served from that same CORS-header tuning directory with that specific script.

We do not apply Moodles or any othe systems JavaScript processing on these, no need to run grunt or any such tool.

NOTE!

We really want to have a local JSXGraph copy instead of relying on a CDN version. We want to make it easy to run STACK in a closed network with no external requirements and having a local JSXGraph is one of the things we do to remove an external requirement.