Test server with refactored code

[Andrey Novoseltsev]

Hello,

I've set http://cosmos.mat.uam.es:8888/ to run the latest development version of SageMathCell which includes a major rewrite or kernel management https://github.com/sagemath/sagecell/commit/dda0fede9d3999fc37e89802355a169536ced96f

If you have a minute, please try it with your favourite code/page and report any issues. Ideally nothing should be broken and performance/stability should be improved, but that's theory. The only problem I am aware off at the moment is that busy spinner gets confused - didn't look at it yet as I was avoiding JS parts.

Thank you!
Andrey